Well, to answer this, there are a couple things to consider.
1)
What are the hours or operation of the bike shops?
Do you plan to ride when the shops aren't open.
2) Are you sure that all the bike shops will always have your tube size in stock.
Seriously, you think they would always have 700x32 in stock, but I've had it happen enough times that it's annoying.
Not to mention the number of times I've settle for using presta when I'm really supposed to be using schraders.
3) How far do you really want to walk, and what is the penalty for being late?
Walking 800 m (1/2 mile) could take around 10 minutes.
In that time you could have already changed the tire.
Do you lose pay when you get to work late?
If this happens too much will you be seen as unreliable, and get your shifts cut? 4)
How much does a patch kit or extra tube and a frame pump really slow you down?
A patch kit can easily be stored in those bags that go under your saddle, or in your jersey pocket.
A pump can be mounted on the frame, and you probably won't even realize it's there.
Personally, I don't think there's much reason not to carry a pump and spare tube.
Although it does seem useless at this point.
I ran over a broken beer bottle on the weekend and heard and felt the glass crush underneath my tires.
Thanks to gatorskins and tuffy tape, I didn't even have a flat.
I seriously question why I should bother.
But then 3 months ago I had a valve fail.
It's almost never the case that I get a flat from an actual puncture, but usually from pinch flats or other unexpected things.
I don't think I've ever had to use my allen keys on my commute, but I still carry them.
That being said, the day you have to walk a mile because you didn't want to carry something as small as a tube and pump is the day you're going to rethink why you don't carry one.
bicycles.stackexchange.com/users/163/Kibbee
There is no unique right answer to this, but I can put it two ways: The way you described (very low puncture risk, good external infrastructure), if it bothers me, I wouldn't carry anything but a good extra tube and a pump.
If it is not an absolute "bother", I would feel WAY more carefree if I did pack a patch-kit.
The second option allows you to change your mind if you want to stray away from your usual route, say, to ride longer, to go to a friend's house, or whatever.
Also, if you don't carry your kit everyday, chances are you will forget it at home when you go out for a non-commuting ride.
Now for the extreme opposite, I definitely would not recommend riding without a spare tube and a pump, EVER!
(But that's also a matter of choice.)
bicycles.stackexchange.com/users/2355/heltonbiker
Think how fortunate you would feel to be able to help a fellow cyclist who happened to get his /her second flat of the morning by handing them a patch to help them on their way.
I believe what goes around comes around, maybe they would help you while walking the 1/2 mile to you bike shop to fix your bike.
Sometimes it is worth taking a just in case item for the circumstance that you just can't predict.
Most of us ride for the enjoyment and a few ounces won't really impact that.
bicycles.stackexchange.com/users/2452/mikes
I don't bother to carry a patch kit or any tools on short-distance commutes.
My rule is that if I could walk home in a pinch, I don't need that stuff.
FWIW, I've had more instances of running out of spares due to multiple flats on long-distance rides than I've had instances of walking home because of a single flat on in-town rides.
bicycles.stackexchange.com/users/2152/Adam Rice
You have to decide the best balance between The disadvantages of carrying a tube, pump and levers and
The disadvantages of being stranded with a flat tyre.
Seriously, that's all it comes down to.
Think about what you'll do if you get a flat anywhere along your commute and how much of an inconvenience it is.
Then compare that to the inconvenience you experience from carrying spares and fixing a flat on the road.
bicycles.stackexchange.com/users/1588/Mac
I'm cycling for urban commute, on well-maintained roads and bike paths, Vittoria Randonneur "puncture resistant" tires, and at no point on my ride am I more than 1/2 mile (usually within 1/4, I bet) from a bike shop.  I also presume that I'll never be without a wallet and cell phone and am in a city with good public transport.  Given that, is there really a reason to bother carrying a patch kit or extra tube with me?
Is a tire patch kit really necessary for urban commute?
bicycles.stackexchange.com
<tire><commuter><repair>
bicycles.stackexchange.com/questions/6215
bicycles.stackexchange.com/users/2288/Larry Gritz
Most people consider carrying a patch kit a sensible precaution. It is a light, easy to carry item that will save time and inconvenience in the event of a puncture. Some cyclists, however, do not carry this item when they are only going short distances and they could walk home if they had to. Consider the inconvenience of having a puncture on your commute without a kit, and the possibility that the bike shops will be closed or not have the right part. While it may be easier to push the bike on short commutes, a patch kit is small and light and provides peace of mind at a low cost.
A simple patch kit is small and lightweight, and provides peace of mind. However, for small commutes it may not be a problem to walk if you have bike prolems. Consider the inconvenience of having a puncture on your commute without a kit, and the possibility that the bike shops will be closed or not have the right part. You may also be able to help other cyclists in similar situations.