I own a 2020 Prime (~28 mile battery). What you wrote is not true. We plug in daily, sometimes 2x / day. This covers all our local driving. The battery is fine. Maybe 5% degradation. I expect it will be good through the 10 year battery warranty.
For longer trips we use the ICE. We've used about 140 gal of gas to cover 18000 miles.
The only rub is that it is so darn efficient it is often cheaper to burn gas than electrons!
And, lest you write back that "you're just one person", I note that your claim that "many drivers rarely plug them in" is not supported. You are probably referencing the ICCT report, which was based on self-reported MPG. To the extent that that methodology is valid, the BLUF is: "real-world electric miles driven in PHEVs could be 25 to 65 percent lower than the vehicle allows."