For so many reasons!
Despite owning a PS2 and a 2.4Ghz PC, I love the simplistic approach of the Amiga's OS and the fact that it is so very responsive. Not only that, the OS has a very small footprint and there's no extraneous features that I'll never use. Beleive it or not, web browsing on my 40Mhz Amiga is faster than on my PC.
I'm not necessarily anti PC or PS2, otherwise I wouldn't own them but there are so many things about the Amiga that still make it a very nice machine to use.