Well, I think Rodja makes a good point, in that if you are using them for regular body training and an adjunct or adding them in for a new twist or whatever it may be, fine.
But PL'ers use them to get stronger and will use them to get the extra level of strength, that may give them an edge. Geared lifters can use them since some of the suits/shirts will take up some load from the bottom, and they need to get stronger thru the better leverages of the ROM.
Squatting and chain work might be one of the tougher to learn, as I use them mainly in pulling/deadlift work, from either the floor or deficits.
From the early days of Arthur Jones, and I am not sure if they were implemented much at Culver City WSB with Frenn and West, but I know Louie et al. seem to make them popular.
That all said, I don't read too much into them and keep it simple, but I am a raw lifter also and don't even use a belt much.
Experimenting with them might not hurt, (I mean even Lou had to start somewhere) and if one is actually interested in utilizing them more in power training, there are some good articles and routines you can find now and coaching with this kind of advanced training is probably worth it if one is really serious about competing on a higher level.
That all said, believe me you can get plenty strong without them, as there were plenty of PL'ers in the 60's 70's and even 80's that never used any of these training techniques. Heisey back in the late 70's pulled over #900 with basic training. Don't neglect simple basic training first and foremost and put the most effort into a handful of regular exercises. Effort and hard work will have you reach nearest your ultimate potential. Not supplements or the newest gadgets or fads. They may give you #20-#40 on top of your lifts, but if you are looking to go from #225x10 to #405x5 in the squat, you gotta put in hard work, focus, effort and determination on a basic routine regularly.