it makes hosting cheaper and deployment easier. you don't need to run a separate server program per app. you share your hosting with others. Sure, things like

it makes hosting cheaper and deployment easier. you don't need to run a separate server program per app. you share your hosting with others. Sure, things like docker have enabled sharing for other languages, but i think there is still more overhead involved, both in terms of system resources and in terms of setup, so other languages can't compete on price. CMS users also (at least in non-enterprise market) don't care about the language things are written in, because they don't use it. but the price of hosting is important to them.