Personally, I wish they they had been around 30+ years ago....maybe my knees wouldn't sound like cereal.
One problem is often what coaches expect of the catcher in the way of blocking. My son's HS coach wants everything,every pitch blocked. So the catchers don't really use the knee savers except when giving signs to the pitcher. So they really don't use them much at all.
Example shown in the picture of the 3 Asian gentleman squatting. Very comfortable position to squat but not good/efficient for catching if lateral movement is needed (heels way too close together,etc. I imagine the flexibilty these guys have developed since birth has some bearing on the lack of knee problemms. I wonder how much damage is done by squatting itself versus the strain of getting up and also continual impact on the knees from years of blocking.
Personally, I like the squatting position shown( particularly guy on far right)to catch with as it offers a good srong position with your butt lower than the mitt. I'm not a big proponent of blocking every pitch(unless situation demands it; catchers get beat up enough blocking the pitches they have to block without getting dinged on a pitch 2 ft outside w/1 out and no runners)but that's what some coaches want ( wonder how many ever caught).
Funny thing about the knee saver is I made an 8 yr old use them intentionally to sit on. No stealing, machine pitch with limited kid pitch situation. The 8 yr old was giving with the pitch (posture was bad)and knocking him back on his butt. So I put the knee savers on and they forced his weight forward onto the balls of his feet as he sat on them. Granted, foot position was a little narrow and mitt position was high but this was 8 yr old ball and all I wanted was for him to get comfortable and get some confidence. Worked like a charm; didn't fall again at all and even got him in an easier position to block with his butt higher and weight forward ( blocking wasn't an initial goal). 8 years later, he's catching HS and considered one of the best catchers in the region...no, knee savers didn't have anything to do with that.
If knee savers make your catcher lazy...you've got the wrong kid behind the plate. He likes the title but not the work that goes along with it.