Because this is that one win scenario among 14 million futures Doctor Strange saw.
As director Joe Russo explains , Q:
In IW, Thanos used the time stone to reverse the time so he could the already dead Vision, and it didn’t cause any time parallax.
Why did no one use time stone to save Iron Man’s life in EG?
A:
It’s because even if you save Iron Man, it will still not change the fact that Thanos will eventually win the war.
Among the 14 million possibilities that Doctor Strange has seen, Iron Man’s sacrifice is a must for that one win scenario.
movies.stackexchange.com/users/27264/A J
If Dr.
Strange tries to reverse time on Iron man, then he also reverses the snap and Thanos would be back again.
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This is exactly correct.
Everyone using the Vision example as to supposedly suggest what Dr. Strange could do for Iron Man are disproving their own theory.
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> Thanos wants to turn back time for stone, but must bring back Vision to do so.->
If strange uses time stone to turn back time for Iron man and undo snap, he must bring back Thanos in order to do so.
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Because there's been more than enough meddling and destruction for one day By the point that Iron Man defeats Thanos and his minions with his own 'snap', there has already been massive loss of life, risk to the Earth, and interferences in time.
There is an argument here that Doctor Strange could re-appropriate the Time Stone and attempt to use it to reverse the physical damage Stark suffered from using the Infinity Stones.
However, if there was any risk that such an action could reverse Iron Man's decisive 'snap', then that risk is simply unacceptable .
Even if Strange was minded to attempt such an action, he would almost certainly have been blocked or dissuaded by the other heroes who would be fearful of re-entering the nightmare scenario of Thanos's invasion again.
The only action that is carried out with the Infinity Stones after Iron Man's 'snap' is their careful restoration to their various points in time by Captain America, in keeping with the original 'time heist' plan.
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In the case of Hulk's damages, Joe Russo told : He's lost an arm (...)
That's permanent damage, the same way it was permanent damage with Thanos: It's irreversible damage.
From that we can conclude that even if Thanos didn't heal himself after the first snap in IW, that suggest that Time Stone can't manage to heal wound caused by Stones themself.
Time Stone alone can't undo what multiple stones did.
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Doctor Strange had watched 14,000,605 possibilities and their was only one scenario in which they won.
Let's assume for a moment that Dr.
Strange did restored tony's wounds, and Tony Stark lives ... what would happen then?
Tony is the 'Futurist' in the MCU and he can't help but keep thinking on how to make the world a better place but we did saw where his intelligence led
(Ultron was his fault and all the death caused by Ultron is ultimately on him.....
Then he forced the avengers to keep together while he could have done that by explaining the future risks he feared and trusting his freinds...and as Cap said that tony tries to win the war before it starts and people end up dying and it's all their fault.....).
I'm not a hater of Tony Stark, he is definitely a great character and its his flaws and mistakes that make him able to learn.
But Dr.
Strange might have saw a danger in Tony being alive.
Moreover, messing with time can break the space time continnum as explained in MCU.
Maybe there is more to the character of Tony Stark than just being alive.
Maybe he can become a symbol or return as a fully independent working A.I
Tony Stark n fill in the gap created by Tony himself.
Hope he returns as A.I though.
Future movies might address this issue.
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At the end of the final battle in  Avengers: Endgame , Tony is damaged from the snap. All the stones are right there, and there are no bad guys left to distract Dr. Strange.  Why doesn't Dr. Strange use the time stone to reverse Tony's wounds?
Why doesn't Dr. Strange use the time stone to do this?
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<plot-explanation><marvel-cinematic-universe><avengers-endgame>
movies.stackexchange.com/questions/99671
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There is an argument here that Doctor Strange could re-appropriate the Time Stone and attempt to use it to reverse the physical damage Stark suffered from using the Infinity Stones.  However, if there was  any  risk that such an action could reverse Iron Man's decisive 'snap', then that risk is  simply unacceptable . Even if Strange was minded to attempt such an action, he would almost certainly have been blocked or dissuaded by the other heroes who would be fearful of re-entering the nightmare scenario of Thanos's invasion again. The only action that is carried out with the Infinity Stones after Iron Man's 'snap'  is their careful restoration to their various points in time by Captain America, in keeping with the original 'time heist' plan. Because there's been more than enough meddling and destruction for one day. 
 Because there's been more than enough meddling and destruction for one day.  By the point that Iron Man defeats Thanos and his minions with his own 'snap', there has already been massive loss of life, risk to the Earth, and interferences in time. Doctor Strange could re-appropriate the Time Stone and attempt to use it to reverse the physical damage Stark suffered from using the Infinity Stones. But if there was any risk that such an action could reverse Iron Man's decisive 'snap' then that risk is simply unacceptable.