This is the modern landscape, but the television example I mentioned (and actually most of the examples I know of offhand that remain successful today) actually

This is the modern landscape, but the television example I mentioned (and actually most of the examples I know of offhand that remain successful today) actually predates the creation of the cable access programs, it originated as an OTA channel pre-cable (in this area). Without actually having researched it too much, I suspect the educational access program is too restrictive for a pivot to PBS affiliate due to service area limitations. You could view the educational access program as a failed attempt to bolster these types of services. There are definitely active educational access stations but I'm not aware of any case where they're still used to deliver teleinstruction - would love to hear about any that do.