Funny Answer: Because boobs. Who the hell doesn't love boobs? Boobs are the most glorious fucking things in the universe. Us Heterosexual Males
* require them for survival at birth, drawing nutritious life-sustaining sustenance from them. Later on in life, we are programmed to copulate with women who show attractive characteristics, including wonderful, lovely, rounded, bouncing, bodacious breasts. Do you not like boobs?
There's only one thing to say to you.
Serious Answer: Because change is slow, but we are seeing more variety in fiction as time progresses because Capitalism caters to niche markets when they're willing to provide money for a service. Also because if you look at
Ancient Goddesses, you will find that significant numbers of them from all over the world--when they take human form--tend to accentuate feminine features even if they're depicted as being incredible powerful, like Aphrodite or Athena. The reason for this is because we (as a species and as a society--biologically and socially) tend to value certain characteristics highly. Among these characteristics is sexual desirability: Not because those who don't have it are inferior people, but because those who
do have it in great abundance are considered to have the positive characteristic of beauty.
You can apply the same lenses to superheroes: They represent the pinnacle of pinnacles, the best of the best, the uppermost cream of the crop. They are what we are generally supposed to look up to as pinnacles of humanity, so we want them to look good. If they don't look good, we want there to be a very good reason for their deformity, to be a message. Superheroes have a lot in common with deities, it's why Wonder Woman is related to Greek mythos and Superman is Space Jesus: He loves you forever and ever and will always be there to save you and forgive you of any
sins transgressions you may enact if you give the appropriate penance. He's even willing to forgive horrible mass murdering villains if they see the right light.
Sound familiar at all?
Over time, superheroes (and heroines) will continue to diversity. If you look back to the golden age of comics, minorities (asians and blacks) were overwhelming villain roles and were horribly stereotyped. Like, above and beyond pretty much any imaginable transgressions of today. Over time this has started to balance out in comics, with heroes either taking an ethnicity swap, or new heroes being made of differing ethnicity that are empowered people. Heck, one of my favourite superheroes is
John Stewart, a black Green Lantern.
tl;dr: We idolize certain characteristics not to dehumanize or objectify, but as things we find most attractive or emboldening in other people. The only sorts of people that tend to get offended by this are also the sorts that tend to stymie progress rather than encourage it through capitalistic means.
*cisgender scum. Refer to your Tumblr pamphlet for additional information.