That's really interesting. I've been seeing similar.
I think what's going on there—at least in part—is a market-size driven decision. There are thousands more startups that are able to use the beginner PaaS model than startups that make it to the point where they can use an advanced PaaS that gives them those options that you need when you grow. (My company does, e.g, ISO etc., but I do think advanced PaaS's are much, much rarer).
It's easier to justify pursuing a market of smaller customers in fundraising rounds than justify fighting established players like RedHat for the massive, blue whale-sized customers. Trout are just more common. And VCs want to see a giant potential pool of trout, rather than a small market with customers that take a long time to close. There is a middle ground but some VCs believe the middle ground is where companies go to die. In my opinion, this bias from the money side of things would nurture new startups and offerings away from the middle and enterprise areas of the market.
The larger but lower-paying, higher churn market is also a well-trodden path and at least one of the leaders in that space has been struggling for a while. So those customers are looking for somewhere to go and these newer companies smell blood in the water.
My 2 cents! YMMV. 🙂