Well, there's a need for certain kinds of researchers in industry. How large that is isn't exactly clear. The difficulty comes to PhD programs when people are able to become researchers without a PhD.

It's also not impossible to become a professor without a PhD. That doesn't make PhD programs useless for that purpose, as long as they make that career path easier to attain.

It's pretty unlikely. In one case there was a tech where I went to grad school, who performed so well that tptb decided she should be a professor. But before they could do that, they felt the pressure to give her a PhD (and where I went to grad school was very much on the "unconventional" end of the spectrum), so they enrolled her in the PhD program, made her take classes, and gave her a degree after she had finished enough classes to cya in the eyes of the accreditors, made her staple her papers together for a thesis, gave her a PhD, and then promoted her to professor.

Part of this was because consider if she decided to leave our institution... There are certainly places where she would have been denied a job opportunity on the grounds that she did not have a degree, e.g. state schools where there are often legally or administratively mandated minimum requirements for professorship and bureaucratic decision-makers who filter out non-conforming applicants before they are even considered.

Also there's lots of government researchers as well. The US has its NIH, FDA, CDC, DOE, USDA, and so on, and other countries have their own versions (if generally not quite as large).