you can run PHP pretty much anywhere, even the cheapest VPS probably has PHP, as well as all managed hosting. For python, go or other languages it can be more tricky if you're looking for cheap hosting / VPS
For average business owners who buy a WordPress template and some 5€ hosting in order to set up a business card web site on their own, on the other hand, it matters a lot. So if your project targets that group of people then PHP is pretty much the only option; anything more complicated than an FTP upload/MySQL import is pretty much to advanced for them and they generally aren't interested in learning new skills just to get a web site online.
The last thing a non-techie business owner needs is to worry about setting up a random server with bad PHP code.