There are pros and cons to any consumer choice. I think users are well informed an making their choice explicitly.
Yes, both eco systems employ lock-in and network-effects to keep customers. And yes that is an issue (separate from the app store issue.)
It may interest you to know that outside the US (and some parts of Europe) Apple has a smaller network share and people avoid the green bubble effect by using alternate messengers (mostly WhatsApp).
There are -choices- which you may or may not like. In the US folk have largely -chosen- to use iPhones despite Fortnite.