I pretty much agree with everything that Aozora had to sayPeople like boobs in anime because a lot of the time they're the kind of perfect boobs everyone loves. If you think boobs in real life, a lot of the bigger ones are saggy and jsut ugly when they droop down. While everyone of course loves big boobs, but they hate ugly boobs.
So what do they do? They of course draw the perfect woman in their anime and as a result we get females like this
Those were jsut 2 examples, there's millions of more. Anime breasts are never saggy, they're always perfectly round, firm and well shaped overall. Also the minimum cup size anyone seems to have is C or D cup. The general cup size is probabaly around F-H.
As anyone can see their figured are completely unrealistic, it's practically impossible for a real life woman to have a figure like that. It's generally a very exaggerated version of the hourglass figure.
Also I'm pretty sure the fact that anime is made in japan has something to do with it. You can't deny that Japanese on average have quite small breasts. while men are always infatuated with bigger ones, so they draw big ones again cause they like them so much. If you compare that to the Americans, how many western cartoons you know where a character has a D-H Cup breasts? I mean sure they're big in western cartoons and comics but nowhere near the size of anime boobies.
tl;dr: Guys like big boobs.