[Ok, so if a man cheats on his wife and nobody finds out (sealed records), is he not a cheater then?]
Under the law? No, he is not a cheater. Especially in the circumstances of an expungement.
[ they might decide stealing cars isn't worth the cost...If they do, they will stay in jail longer.]
I assume you mean they will go back to jail? Still nothing changed under SB91. So I ask again, what difference is there from what you are advocating in regards to law enforcement/deterrence/rehabilitation except the matter of how soon someone has the opportunity to break the law?
For all intents and purposes there seems to be nothing in what you advocate unless you are including imprisoning people solely on their character to prevent giving them the opportunity to break the law. Unless you have a plausible alternative explanation I'm left to assume you are just advocating a change on a purely emotional basis.