It's mostly about nostalgia for me, and it's fun to play with vintage hardware, takes me back to a simpler time. For my day to day work I use a modern Win7 PC but Amigas are fun. If it doesn't excite you anymore then sell the hardware to somebody else and let them enjoy it, I'm not going to try to convince you to keep it, either it interests you or it doesn't. There's nothing you can *do* on a vintage Amiga that you can't do on a modern commodity PC, that's not the point.
Yeah I don't get why anyone wants to play Quake on an Amiga either. The Amiga was already long in the tooth by the time Quake came out, an old Pentium II with a Voodoo card will give a far better Quake experience for a lot less money.