Because we already know how silly Dante looks. Are you telling me Dante can't be made fun of? Just how at his looks in DMC 2 and 4. The jokes for that kind of apparel basically write themselves. DmC was looking to establish a more contemporary setting so seeing him adapt to that kind of setting is expected. Brokeback Dante from DMC 4 would definitely be out of place here and look stupid.
I do not understand your logic. For one, Dante in DMC
is cool:
If you just look at DMC 4 Dante and go "Well he had cowbow chaps, so not cool!", of course then he's not cool. But even goofy Dante from DMC 4 is funny as hell - and that makes him cool:
But there isn't ONE Dante, and if any of the Dante's is more Dante than others, its DMC 1 Dante. And as you can see above, HE IS cool.
Now Ninja theory's vision to create a DmC with contemporary setting doesn't make Dante not cool. It just means Dante from DMC isn't meant to be in a contemporary setting, it says NOTHING about Dante not being cool. For instance i could place Kain or Raziel in a contemporary setting and say "Well herp derp they are ancient vampires therefor they are herp derp not cool herp derp".
It's such ignorant logic to put a videogame character into a realistic setting (that clearly was meant to be in a unrealistic setting) and say he isn't cool because he doesn't fit into that setting.
It's even more ignorant to expect that Dante from DMC wouldn't have modern clothes if he lived in a modern world.
And if Dante doesn't fit into the world of DmC, then why do we have these:
A half angel/half demon who has a sword, two guns, white hair. Yes DmC Dante is very fitting for a contemporary setting. I see DmC Dante's on the street everyday.