Some of the apps are emulators, which were derived from game systems that each emulator mimmicks. Some people like the idea of playing such apps on a TV screen as the systems emulated were traditionally played via console inputs and watching the TV screen. For many using a PC is ackward for games that just boot up and play. Porting some specific apps to Wii simplifies the process of having to do menial things for the PC app. Basically it's all for the simplicity factor, and possibly nostalgia of playing the games on a TV screen as they were originally intended.
Other apps I can probably see your point. Like 3D engines to build games, and such with, however some people like to do things that were unthinkable on other platforms so a program that can achieve that is ported. Albeit not all apps are portable, due to various, but those that can be used with the Wiis power, and take advantage of it without being too powerful are always candidates to be ported.
The best reason people dont choose to homebrew PCs is the fact that people have been homebrewing PCs for years. Emulators are a prime example of this. As are ports of Doom such as Zdoom, and GZdoom among various others. Their function to do things above the scope of the original Doom engine is what makes them homebrew. Another reason for a seemingly "not a lot of PC homebrew" is the fact that a PC has a ton of different programming languages. One known as LUA could be considered a homebrewing language as you can make a game, app, or w/e just with it alone, and it's simple enough to learn that anybody could use it and make their own program or whatever.
Anyways I dont know much more to explain it any better, but basically if you look outside the box of the licensed software you buy for your PC then you'll see more things that came from homebrew on it.
Edited 2 time(s). Last edit at 08/31/2010 02:56PM by nightwishfan1.