A few reasons. Things like gradients and other skeuomorphic components that are usually jpegs look horrible if you don't have fallbacks for retina. The screen is brighter and crisper, so those vector buttons look great. etc.
My girlfriend has, I think, an android 2.3 phone. Flat designs are HORRIBLE on it. However, they look crisp on a retina phone, so much that it actually look like the screen is made of physical (material) components.
As for people liking it or not? That's just a trend. We are going back to skeuomorphism in a few years, mark my word.
