Why deprecate ES2 instead to migrating on Platform Extension??

Hello there! I wanted to make a little question.
I want to use Unreal Engine to make a game that I can play even on my phone, that supports only ES2, even if recent low end phones supports also ES3.1 . But I was biased at the announcement to deprecate ES2 instead to moving on Platform Extension, even if some famous UE4 games, like Lineage 2, PUBG Mobile and Call of Duty Mobile support also ES2. So, I just want to know, if possible, the reason over that decision. Thanks in advance!