They don’t really have the right frequencies available. In the GHz range they operate point to point comms at ground level with low powered radios wouldn’t be a great experience except for if you were so close to someone you could practically shout at them.
Amateur Radio and GMRS though are still very much things that will give good performance for those use cases. GMRS requires a “license” but no skill is required, just payment to the FCC.
Ham radio or GMRS are still great options for remote areas or at crowded venues where nobody can get cell service because everything is overloaded.
The frequencies that walkie-talkies use are available for walkie-talkie use. Sure, it might need another antenna, but so do features like mmWave, UWB, and Satellite SOS, and I guarantee a genuine walkie-talkie feature would see more usage than those. iPhones already contain antennas for dozens of bands including 600 MHz. I don't see it being infeasible to add ~465 MHz band support.
Unihertz even makes an Android phone with a DMR UHF transceiver, the Atom XL.
https://www.unihertz.com/products/atom-xl