I have a US Passport that took less effort and paperwork to get than a Real-ID. I will never submit.
It proves my identity as a US Citizen as much as it has to be.
Unlike most driver’s licenses, a passport card doesn’t expose one’s address. This makes it a great form of ID to use in non‐airport situations as well.
Coincidentally, this is also how it works with German passports. You're legally required to have either an ID card or a passport (or can have both.) The former has your address and comes with a bunch of ever-changing digital signature/ID features (that you need a special reader or app for). The latter is just a biometric (still RFID but well) passport, with only the city (issuing authority) listed.
You're totally right that drivers license and passport ought to be sufficient documentation to get a real id, at least for US passport holders or for foreign passport holders when suitable evidence of lawful status is physically present within their passport. But that's not how the real id rules are written, since two proofs of the address of residence are also required. Not all non-real id drivers licenses prove residence (as opposed to for example mailing address), and at most, driver's license plus passport will provide one such proof and not two.
Documentation of the Social Security number, such as a Social Security card, also used to be federally required. Although this requirement was removed, nothing forced the states to remove the corresponding requirement in their own state-law rules, and some states still retain that requirement. Providing any Social Security number you have been assigned is still federally required, and the number is still verified against SSA records, but the feds no longer require the applicant to provide proof that it's their number.