Just can't see a reason to have those. Just me though
It's not just you. Those things are a pain in my balls. If they didn't provide such excellent shade on the western exposure of my house, I would chainsaw those bastards in a heartbeat.
OP: Cut down the weak one and then eliminate the other two so your back yard doesn't look uneven. Fail to do so, and you will be hating life when those things get big. Two months of falling leaves that have a knack for getting stuck in every other kind of bush (have to manually remove them...a blower won't work), those dingleberry things they drop, ah, frick the bastards!