It gives the widest amount of people the chance to selfhost for cheap.
You can get a PHP webhost for $5 per month including databases, some cheaper, some more expensive.
You dont have to worry about a VPS, Docker, Kubernetes, or anything like that. Hosting companies contribute by having "one click installs"
Sign up, pay you bill, click a button and you have your very own Wordpress instance and you can publish what you want.
If you create solutions that you want people to be able to self-host it is the best choice for now.
It is far from perfect.
WP has suffered a long string of severe security bugs. People have gotten their sites hacked
Some cheap hosters are not good. (I had great experience with a couple)
A lot of devs like to hate PHP and see it something awful from two decades ago. I understand that. There is truth in it. PHP from 20 years ago is quite different from PHP now. It is probably better than you think.
I would not start a project that needs to Google scale on PHP.
Nor would I expect a lot of people to have the ability to cheaply and easily self-host something like that.
but I like running my own Wordpress, my own file share solution, my own wiki and so on.
I can do all that dirt cheap thanks to awesome developers, PHP and cheap hosting.