Stuff like that should be optional. It's like a kid saving enough money to buy an HD TV and then buying an analogue black & white one instead and forgetting the HD one altogether. You can do that but it's not for everyone. I have a fondness for the classic series but I don't want the new games to look like that. Some people do. Which is fine. But that shouldn't stop new games from looking much better than an NES game.
It can be done better, why settles for less? It's things like that, that some game companies use against the consumer. They can say stuff like "We need a new game. Oh, just make something really quick and slap mega man all over it. As long as he's on it people will be happy. They'll buy it." It's because of stuff like that that a great thing only turns out to be a slightly okay thing or worse.
Because money. Making it the way you are suggesting, would essentially be making two games. One of which would be harder to make. at that point, they might as well either just make two separate games, or make one or the other. And when it comes down to one or the other, they would go not only with the cheaper one, but the one people are most likely to easily accept.
I had to do it. It really bothers me many people (not just here) want new MM games in 8-bit style. We can have both old and new damn it. Why settle for retro only? Or use the Sega Genesis style graphics from the Wily Wars at the very least (and I wasn't a Sega fan back then mind you).
Its honestly 2 things.
1. personal preference,(such as how important the look/graphics are to you,)
and
2. (posibbly the most important) what era you grew up in.
Many people grew up with 8 bit Megaman. I mean, there were 6 8 bit games, and only 2 that were higher graphics. 8 bit defined many peoples childhoods, and some of them shunned the newer ones like 7 or 8. (there seems to be lots of 8 hate for some reason)
So its only natural that given the option of more childhood nostalgia, they would choose that. And Capcom knows that. they know that it will sell. Why risk it all when youve got a formula that not only does Inafune want to revisit, but a portion of the fanbase does as well?
I myself grew up in the 90's. So I grew up with the PSX Megaman Era. THAT was what defined my "Megaman Childhood". So Im more biased towards it, and I can understand how older gamers feel about their NES megaman childhood.
The only real difference though, is I would actually prefer new graphics over retuning to older ones, (that includes the PSX ones)