Why are more and more websites increasingly operating subscription models?

[No idea if this is the right community so please forgive if not]

More and more I am noticing websites charging for subscription services, whereas years and years ago I suppose when less data was being sent and received [in the days of lower speeds etc.] most websites were free. Youtube is a particular example - now they are offering Youtube Premium whilst introducing inconveniences for free users. Amazon makes less sense to me as surely they profit enough serving as a shopfront, but they have also introduced features such as Amazon Prime.

Apart from the obvious - because who doesn't want to make a profit - why is this? I would be interested to get some insight from people knowledgeable about this kind of thing as I am only a user and can only guess.