you are looking for a good reason? Let me try to give 1
It drives up TL traffic. ;)
I bought a 1000$ guy before last scrimmage, only to get 5 players on the field.
I could have just played my four, and have a lucky fan play, but I hate it that my valuable fans would get injured during play, so I decided to spend a 1000 on a player. I call it "lucky player" since otherwise he would have spend his last miserable days on the TL. Now he could end in glory, playing with others he was worshipping anyway, ending his career with a glorious win.
But I know you are right. If the BBs have chosen 3 is the number, then they either have a good reason for it, or thought it was a nice number. And unless there is some real good reason, I don't see reason to change it (read put time and effort in it).
On the other hand, if a majority of the BB-users would like a change better, that would be a real good reason. Not sure where we stand on this point thoug.
They are not your friends; they dispise you. I am the only one you can count on. Trust me.