Because they don’t have that much initial money in their pocket, while the idle computer is already there, and the biggest friction point is convincing people to install some software. Both producing rhetoric and software are several order of magnitude cheaper than to directly own and maintain a large fleet of hardware with high guarantee of getting the electrical stable input in a safe place to store them.

Assuming that getting large chunk of initial investment is just a formality is out of touch with 99% of people reality out there, when it’s actually the biggest friction point in any socio-economical endeavour.