Cause original games sometimes don"t work with not "up-to-date" systems ?
The Wii, for example, or I least, I don't know how to do.
I bought "Punch-Out" original disc and my 3.2 (E) Wii didn't wanted to run it, so I had to run the original disc with a backup launcher (Wiigator's Gamma Backup Launcher), and so I wondered why the point to have bought the original if I had to use it under a backup launcher). And I think I got some luck because if the original hadn't wanted to run with the Gamma Loader, I would have been screwed and just had lost my money).
This is, personally, the reason why I won't buy New Super Mario Bros for example. I don't want to buy the game and finally see it won't work on my system without any tricks/modifications (and this time, it's not even sure the original would work on NeoGamma Backup Launcher if it has a copy protection or whatever on the disc).
And no, I don't want to update my Wii, some homebrews (like emulators) are nice and I don't want to bother myself with lots of upgrading steps (which have always some risks to screw everything) to make them work again.
About the DS, because the cart port of my DS is broken ? (It's just easy as it). And that I don't want to buy a new DS just for that (My Wii also have his fan broken, had to buy an Intercooler, Nintendo systems really seems to become cheap in terms of hardware quality compared to 80-90's years, as some of them also got some dvd drives problems with Smash Bros Brawl).
When there aren't any homebrew on a system or if I don't have any problems with the system (hardware problem or update that remove some things I want), I only buy original games like on 360 (had more than 40 games on it) & PS3 (add more than 15 games on it).
Here's for me.