It's not hard to pick up an extension off the floor. It's also not hard to lean one against the wall. The bucket I use holds tons of paint, is very sturdy, easy to carry around, easy to cover for as long as is needed. None of that applies to trays."its easier to pick something up off the ground than from a handle at waist height"
thats your argument
But if you like to do things another way, that's fine. Whatever is right for you is...well, whatever is right for you. I'm just sharing how I prefer to do things. You can do the same.