People are gonna give you crap because that's what they've been told.
Here's a confession, I started playing NL as a shortstacker, and
I think shortstacking has its merits.
A lot of people will tell you, Oh you're missing value!!!!! blah blah blah. What they should really be saying is, "You're missing value
if you're a better poker player than the other deep stacked guys.
Shortstacking has some strong advantages. Most of your opponents are used to playing ~100bb effective stacks, well every hand against you is going to be 40bb stacks, so you're moving them out of their normal zone.
A LOT of players will give no credit to a short-stacker. Oh he jammed? That guy was sitting on 40bb, he's an idiot, I'll snap him off.
You can't be outmaneuvered postflop. With a short stack you're either committed or you aren't. There's no threat of future bets because the chips are getting in or they aren't.
Along this same line, you're dealing with earlier commitment decisions, and shorter
hands. This makes your strategy more cut & dry, you want to hit big pairs and put the chips in the middle. I would add flush and straight draws that happen to occur, but I'm not playing suited connectors, those things need lots of implied
odds and we've reduced implied odds significantly by playing a short stack right?
So if you feel you're playing in games in which the players outclass you a bit, there's no shame in short stacking. However I would urge you to seriously read up on proper shortstacking strategies. Please don't sit on 40bb then play poker based on how you've read on forums you should play, because you'll be throwing away money.
You will be giving up an edge if you are the better player, or if players are calling wide. If you can value bet someone for three streets with top pair, then you're giving up some expectation.
Also you've handcuffed yourself a bit, because just as your opponent cannot scare you with a big bet looming on the next street, so too is your threat removed. Your opponent knows you only have 40bb total to bet, so your ability to force a laydown based on future betting is hampered.
Like I said, if you're going to do it, learn to do it right. And once you feel you have the edge on the other guys, you should definitely go full stack.