Nah, it’s mostly because all the tech reviewers trashed phones with plastic backs saying they felt cheap. If you look at any of those reviews they always talk about the premium feel.
It also changed from aluminium to glass backs mostly for wireless charging.
Plastic backs are better, but the tech reviewers did a lot of damage there. If they’d tried to influence people and explained why particular made sense instead of trashing it we may have more plastic phones.
It's time to stop thinking plastic phones can't be premium (www.androidpolice.com)