Because playing Blu-rays or DVDs makes playing games harder? I don't understand? If you don't want it, don't use it. But I have a big Bluray/DVD collection and I appreciate having those features.
No no, I wasn't attacking the ability to play movies, I meant (like MadeMan said) that the less operations and moving parts, the less opportunities the system has to fail. Like MadeMan, I don't know if this is true or not, however I see many more working systems from the third through fourth generation than I do from the fifth onwards (the Dreamcast being an exception).
My XBOX and PS2 both have disc tray problems despite only being 8 and 9 years old respectively. Meanwhile my junker Saturn has lasted 15 years problem free and my Genesis still feels brand new despite being 20 years old. Same goes for my Game Gear, Nomad, Pico (lol) and previously mentioned Dreamcasts.
I don't know how reliable GameCube's are nowadays, but I'm guessing they're reliable. Probably because they never get played (I kid, I kid).