Also rooting is a non-solution for many people, even if they know how to do it. Many banking apps refuse to work on rooted phones, and the apps are often required to use the banking services. My experience on this is restricted to Germany though.
My understanding is you can get around that with things like:
• Magisk: https://forum.xda-developers.com/apps/magisk/official-magisk...
• Xposed: https://repo.xposed.info eg https://repo.xposed.info/module-overview?combine=bank
I believe that reliably rooting is
* Not an option for the general population, * Not desired by large parts of the general population, * An option taken by people that are more willing to try alternative apps anyways. * Counter to people that just want a system that works.
While preinstalled apps target the general population not willing to change but may be willing to try things they already have anyways. The motivation is the same for google to have their apps preinstalled (even forcing OEMs to install them when all the OEMs want is the play store).
Overall I think: forcing preinstallation is an attempt to support local companies and cost foreign ones users. For this the (small) group of people rooting their phone is probably irrelevant.