Compatibility marks/certifications like AirPrint (2010) define how to advertise your IPP printer and its features, such as whether you can directly send a PDF. IPP Everywhere is perhaps the most notable open alternative to AirPrint.
That exists, it’s called IPP.
The PostScript was created by ex-PARC people as they were founding a small startup called Adobe Systems, and it was chosen by Apple for its revolutionary 1985 LaserWriter printer. LaserWriter was partially OEM'd by Canon, and its competitors couldn't simply steal the protocol; most others to date use a 100% compatible proprietary protocols that, IIUC, aren't internally that much different from it. And PostScript later became the basis for Adobe's other publishing data formats, including PDF, which means pdf/ai/psd is 100% guaranteed WYSIWYG. macOS 10.x also partially uses PDF to render desktop.
and this ^ is why.
Nothing about what the parent wrote prevents that.
Installing the specific driver like it's 1999 works well, but most people don't bother these days. And thus the world is a bit more crap.
[1] ie a risograph
It costs more money to make a printer with good firmware, and you're more likely to throw away a buggy printer and buy a new one with new special ink cartridges.
It's not just firmware.
Printers are hardly "complex" - a few very standard gear/roller/sensor based mechanisms we've built for 4 decades pretty identically with hardly any innovation. Besides far more complex frequent-use devices don't have such shit problems and experience.
Nor is "you're out of blue ink, you can't print this b&w document" or "you didn't install the official $50 cartridge, but a third-party $10 one, you can't print" and such crap related even remotely to printers being "complex robots" or "requiring frequent supply reffils".