Why is it standard to reset to knees after someone is tapped?

Perhaps pure lazyiess or to catch a breath(do that in between rounds)? Why wouldnt it be more ideal for improvement if you went back 1-3 steps to work on the battle leading up to that point? at least until you are at the same level as your partner. The only other excuse would be if you went into that role intitially with something else in mind to work on. Anyone here ever roll without resetting to the knees? If not whats your excuse?

I don't think that is a standard. The only time I start from my knees is when the mat is too full and coach says no standing to avoid collisions or if I am doing drills from that position.

I think it has to do with crowded mats. If there is room for everyone to work standup I think that would be the norm.