That only has appeal to purists. Why would Joe Schmoe care that their phone is made by the same people who make the OS? And why would someone buy Android for the iPhone experience?
To be clear that appeals to me, but I'm not the average consumer. And despite that appeal I have a S20+ because when it came time to upgrade Pixel was still stepping all over itself with poor battery life and weird features that I didn't need. The 5's now offers no "flagship" option, which are the phones that appeal to me. I hope that they can get things sorted for the next time I want to upgrade.
Samsung has marketed well and makes high quality phones. It hit the ground running with Android and hasn't been afraid to reinvent itself (OneUI was a greatly improved experience).
To be fair that is available for all US carriers at this time. I've had RCS working on Mint(T-mobile) and now Visible(Verizon) for years.