Like nearly every decision in life, it's a cost-benefit analysis. And "cost" meaning the negative aspects, not the monetary price.
For example, I always play with a full cage. I got used to it playing over the past 30 years so the cost is relatively low to me. And the benefit is quite large. I get hit with a stray stick or puck or something at least a couple of times a season, so probably every couple years I'd be needing to get stitched up or visit the dentist. So low cost - pretty high benefit, to me personally, of wearing a full cage, so I do.
The benefit of very protective shoulder pads (high end) is not much more to me than lighter, more mobile pads. Random cross checks, collisions, deflected pucks, etc. are handled slightly better by nicer shoulder pads, but typically only marginally so. And so usually the improvement is a smaller bruise. I do find the cost of mobile shoulder pads to be relatively low and well worth the benefit they provide over nothing. But the cost-benefit of moving up to more protective ones is not generally worth it, to me personally.
I do make an exception for certain games/tournaments that have a higher number of let's call them "aggressive drunkards". I do wear high end shoulder pads for those games. And the only moderate to serious torso injuries I've experienced as an adult were in these games, while wearing good shoulder pads: a cross check to the spine between the shoulder pads and pants that hurt for a couple months, and a cracked rib when a player suddenly decided checking should be allowed.
If I really wanted to minimize my chance of injury as much as possible, I'd just stay home.