It seems like most routines call for sets of 5 reps. Is the 8-12 rep set completely dated or does it still have a place?
Personally, I think doing many reps of squats is so tough on your general endurance that the endurance will be the limiting factor, not muscle strength in the muscles I want to target, it will also make you much more tired during the rest of the workout, which is bad if it's part of a whole-body workout.
Also, deadlifts, and to some extent, squats, are so critical to get right form-wise that many people keep the reps low to be able to get push themselves strength wise while maintaining good form and not injure themselves.
Third, programs like starting strength that mimic powerlifting are "in" right now. People want functional strength, not those body building muscles that obviously aren't functional at all... ;)
The general answer towards rep ranges has been written about previously, and it's fairly proven.
But since you're asking about squats in particular, I'd offer this up:
- The Madcow 5x5 (non Olympic lift version of the Bill Starr 5x5) program has a set of eight reps to finish up the intensity day. So even on classic "5x5" programs, you'll still run into reps higher than that.
- I find the higher rep ranges good for warmups and fiddling with your form. At your 5RM (the most you can lift five times), you really shouldn't be noodling around playing with your form. At ~10 reps, the weight is light enough that you can adjust some things and think about more than total concentration.
- In one of his books Mark Rippetoe talks about doing 20 rep squat sets, and they are indeed brutal. I don't know if there's a place for them if you're on a dialed in training program, but it's something I toss in every now and again just to remind myself what they feel like.
My fundamental disagreement with hypertrophy training is that by going for strength your not going to end up being "small" and benching 400 pounds while pulling 600 off the floor, and squatting 500 on your back. Plus, the path to such strength gains is in the wake of professional athletes. This is in contrast to the rather steroided/injured/chemistry experiment that makes up most body building.
In no way am I implying that every bodybuilder is on gear with torn rotators, but you don't hear about a lot of strength athletes dying in their early 20's in a Thai bath house. You can be a natural and safe body builder, but the gyms of the world are littered with broken connective tissue and substance abuse from the pursuit of "aesthetics".