Actually, no, it is entirely clear: it is because the copro-grammers ("writers of feces") who produce this stuff have no respect for the users. The same utter disrespect underlies the recent bloat in iOS apps:
One Friday I turned off auto-update for apps and let the update queue build up for a week. The results shocked me.
After the first week I had 7.59GB of updates to install, spread across 67 apps – averaging 113MB per app.
Okay, so maybe you say who cares, you only update apps over wifi - but do you only browse on wifi? 14 MB for a few hundred words - that adds up fast.
My house, my rules. I look forward to iOS 11, and enabling every blocking feature I can.