Edit: Another positive aspect of legginess is if you want to graft (not the sort of grafting where you take a root stock and graft a scion on it) a few seedlings together. You can just twist a few of those seedlings together and then bury just below the cotyledons and keep on twisting them together. That might be a fun experiment for you if you have extra seedlings. I'm having a good time with two naga morichs I grafted together as seedlings. I just put them real close together and kept twisting them as they grew. I didn't have to use anything to tie them together. However, you may want to tie them together if they don't want to twist.