Are you sure it's not trolling? At the very least, it's a stupid question.
Nobody is saying that playing them on Wii U is better or the preferred option, though there are some positives: it's generally cheaper to buy the roms than to buy their physical counterparts, you can play on the semi-portable tablet thingy (bonk while pooping!), and they'll look good on a big lcd without needing an rgb mod, expensive upscalers, etc.