Very few developers are lazy, the sooner you get that toxic kind of thinking out of your head... the better, trust me.
When corners get cut, it's cause it was a time factor. They only have so much budget to do things, they have to prioritize. You can call it "being lazy" but really that just tells me that you lack experience in that kind of work environment.
OT: As for game sizes, more information equals more bytes, bits, bips, and boops... which equals to larger sizes. You only have so much time to dedicate to finding clever ways of cutting detail, without cutting detail. These developers have found amazingly ingenious ways of cutting down on size. Now it's up to compression to get better and we're finally seeing that, slowly tho. Data compression is not easy.
Everything has gotten larger. Movie files, song files, Word doc files, Photoshop files, illustrator files... data/information.