I was writing them email templates 15 years ago... oh... look we are still using tables. How has email markup not evolved?
See https://www.caniemail.com/scoreboard/ and take note of what's at the bottom of that list.
We just need so called "Kobold letters" to catch on so that all the inconsistencies become an actual threat. I'm only partially joking.
Also humans seem to need fashion as a mechanism to show belonging and distinction. (Differentiate form parents generation, show affiliation to some sub culture, ...)
And then there is the hope to make the production more efficient. (Which may not work out)
I guess Google tries/tried with AMP but it's not that and I doubt they have the resilience to keep the effort up for decades for it to catch on.