Depends on the service. If the company sells to developers, or requires developers to extend their customer base (e.g. Stripe) they will put more effort in. If developers seem incidental to their service and customers they may not (e.g. Zoom, Google Drive).
Comments
I think this is already happening. I commonly compare API services based on their docs.
For my own API business in particular, I've had numerous customers tell me they chose us because of good documentation.
Depends on the service. If the company sells to developers, or requires developers to extend their customer base (e.g. Stripe) they will put more effort in. If developers seem incidental to their service and customers they may not (e.g. Zoom, Google Drive).