These arguments are often interesting, looking at it from the outside.
The reasons given are usually based around fear and negativity… e.g., “if you don’t go to depth, you’ll get injured”, or even “if you don’t go to depth, you won’t get ‘proper’ development”, or “it won’t carry over well to [insert whatever]”
It’s just odd that the approach is basically to scare people into going to parallel or lower.
And it’s even more odd that those arguments don’t really have much substance to them anyway. If you lift weights, and actually push yourself to get better at it, you’re going to get injured. Whether that be major injury, or just niggling pains, you’re going to get injured. I could sit at home and play video games and not get injured, or I could go out in the gym and expose myself to that risk. These are things that I think every beginner should also come to terms with – you might as well be upfront with the potential costs, instead of suggesting that there’s some easy low-risk way to get their goals. I really don’t think that’s a good lesson to teach anyway.
As for the others… well, what is “proper” development anyway? There are people who’ve done quite well aesthetically without ever really squatting. As for carryover, well, squatting more or less to depth is really not nearly as important as just actually practicing your activity.
Obviously that doesn’t mean to be stupid about things. There are definitely ways to do things that are less likely to lead to injuries or whatever, and I think spreading that information is helpful. But present it in a positive light and as choices, rather than trying to scare people into doing things a certain way. Most people are intelligent enough to make a decision, given options and information.
Squatting to depth will develop different muscles in different ways than not squatting to depth. If you care about maximally developing those muscles, and you’re neglecting them with your training (whether you’re squatting or not), then you’re doing something wrong. If you’re ok with that tradeoff, fine.
If you’re an olympic lifter, for your sport, it’s pretty useful to learn to do a good ATG squat. If you’re a powerlifter, for your sport, it’s pretty useful to learn to do a proper parallel squat. If you’re just looking to get bigger and stronger, and whatever you’re doing is getting you bigger and stronger, keep doing it.
Squatting with “proper” form is by no means a safety net from injury or inadequate development; there’s really no need to present it as such.