Pro bags are designed as they are for a very specific purpose, and that doesn't always fly with what the needs are of the general hockey player who lugs all their own equipment around. The size is specific for packing all the bags together, but also a lot of the stuff we carry around with us doesn't even go in a pro players bag. All of the team laundry is in a laundry specific bag or trunk, skates typically are not even kept in the players bag, they all go into a trunk or specifically made bags to carry the teams skates. Think about the stuff we take with us, tape, maybe a couple of tools like a screw driver, blade stone, etc...none of that goes in a pro players bag. It's literally just their equipment and their toiletry bag. So for them it makes sense to have it be one compartment
You can take it one step further and think of it from an EQM's point of view, they have to unload 25 bags at 3AM, if everything is in individual compartments, how much time does that add to their job of unpacking...then when they have to get to their plane after a game, is it easier to just throw everything in one large bag or putting everything into specific compartments?
For me personally, I use an Eagle Pro bag, then I have two toiletry bags...one for shower stuff, one for tape/tools/etc. My laundry bag, then the rest is just equipment. Works well for me. The small square size of the bag works great for packing in my car (especially when carpooling with a couple of my teammates) and great for flying.