On the occasions I play on a pitch that allows it in the season I'll always bowl bouncers, whether to force a batsman back or sometimes because I'm angry ha, so I bowl a few in nets. Good to face them too as you do get bowled them outdoors. There's no point overdoing it though as you do see some people doing or you'll get yourself in trouble when you get outdoors. As others have said though, if a batsman (particularly if they're a good player) is just slogging across the line rather than batting properly then they'll get some reminders! Remember when I was at uni there's was a county 2s bat who'd come in to the club training and slog everything, not talk to anyone and go and do fielding practice away from the nets rather than bowl, before leaving early. The nets were rapid so quickly decided to never bowl anywhere except at his head.
Don't bowl bouncers at your own tailenders in nets though, don't be a dick!
Often as not the problem isn't some bloke being a pillock and bowling too short though, it's the surface. Most amateur quicksilver miss their lengths and bung one in halfway down sometimes, difference is outdoors is usually sits up and disappears rather than flying through like it does in some nets. Also, on a personal level, if I'm not bowling with a newish ball outdoors I mostly try and hit back of a length. I'm tall and bowl an ok pace, so in some nets a lot of it can end up coming through chest high, and while you do try and adjust sometimes you end up with a batsman throwing the toys out the pram! Moral of the story is, super bouncy indoor net surfaces don't provide good practice for amateur cricketers - bowlers or batsmen.