dave said:
Primarily it is to avoid the situation of one person joining late in the trading, offering up just a few items, and swooping up dozens and dozens of offers with the vast amounts of tickets that are given late in the game.
I agree with DnD. Coming to the game late they may they be able scoop up a lot, but they are still getting the same number of tickets as everyone else. But everyone else got to pick from the start and get all the choice seeds. There is nothing stopping someone from coming in with just a few items at the beginning and picking a lot. We can post rules that say they must have a minimum number of packs or varieties, but there are no computer controls in place to enforce the rules. It's up to the host to count packs and varieties which could be tough in a large swap.