Because the resources required to run an overlord-level AI require a megacorp to fund them, and a megacorp to run the data centers (plural) needed to operate the neural models.

Open source models running on local hardware serve the needs of individuals and do what you want. But you're not going to be able to provide or gain access to much beyond what you can pay for. Megacorps like Microsoft, ABC, or Apple can pay for an awful lot.