When word got out that Mega Man 10 would have an easy mode, well, you can probably guess what ensued over the internet.
"Easy mode? How lame!"
"Only noobs play on easy!"
And so on. At times, I think it escapes many that not everyone is of the same skill level. I was pretty scrappy at Mega Man games when I first started out some 20 years ago, but I managed to improve. That being said, for all my adeptness at previous Mega Man games, Mega Man 9 was pretty hard, much to the point that I feel that Capcom/Inticrates focused on the difficulty above all else.
I wasn't the only MM fan that found the game's difficulty to be frustrating. I've said it before and I'll say it again, I don't mind a challenge but there's a difference between challenging and just stupidly hard. They probably realized that MM9 was too difficult for some players, thus the reason for easy mode. Why should other players be denied a good time with a MM game just because they don't have 20 something years of MM experience under their belt? These same people that mock easy mode are probably the same ones that will get their junk handed to them in other games.
It's nice to have choices and I wouldn't be surprised if more than a few players actually play the game on easy mode.