Because PWAs are mostly hype originally aggressively promoted by Google, but now even Google is tired of promoting them.

One of the few places where hype is still real is Hacker News, and even here people can't even come up with examples of good PWAs beyond, and I kid you not, Twitter.

Going from 1 install to 270 installs is a 270% increase, too. So I would take such stats with a grain of salt weighing about 270 tons. Google is dominating mobile market and Chrome is dominating the browsers market, and that's the best stats they can come up with?