A smartphone from Google or Apple is also pretty much required for certain government apps, banking/financial services, and so forth. I wouldn't call it a stretch to say that in the future it would be mandatory to have these duopoly controlled devices on your person at all times, like how you need to carry an ID card.
Many of those apps don't work on rooted phones or custom ROMs without workarounds and doing so is a TOS violation in many cases as well. Also imagine what it would be like if your Google or Apple account got banned by accident with no human support to sort it out.