Christ’s sake, we are talking about guys/lasses on their third degrees who have shown talent.
In the UK even undergraduates don’t share rooms, but you need to remember that a UK undergraduate degree is not taken by school kids.
Both of my Economics tutors did consulting, both are now rather well known, I can’t say that I don’t feel sorry for the 3rd world governments that they worked for.
In the UK the academics set university policy.
To be honest, while they have their limitations, they are less destructive than the alternative.
I’m still not getting this. Not that it matters, but we’re likely having a cultural disconnect here. In the US, “undergraduates” are people, mostly aged 18-22, going through their first four years of college and, if they live in a dorm, it is quite likely that they have a dormmate. If they don’t want a dormmate, my school offered the simple expedient of allowing it - as long as you were willing to pay double room fees. 
“Graduate” students and “Professional/Advanced*” students usually don’t live on-campus unless if they are single, other than for financial reasons. For example, Harvard Business School resident halls are limited to single students - if you’re married, you must live off-campus.
Not that it matters as many Grad/advanced students work full-time careers while they go to school and people in this situation tend to have their home-life relatively settled. I received my MBA this way: had a job, wife, home, baby in the house, went to work from 7:00-5:00, then went to school from 6:00-9:00/9:30 (and most every Saturday for 8 hours a day for a year and a half). I can’t think of a single person in my class who lived in student housing (of course, it was a professional MBA program, designed for people who already have on-going careers).
*I.e., people going for their Doctorates, PhD’s, Law degrees, etc. (which is what I think you mean by “third degree”).
Not at my university they don’t. Managerialism is rife in the UK University sector, the recent happenings at Oxford notwithstanding. Whatever decison making processes look like on paper the VC and his/her officers hold the power.
Maybe, but running simulations of the effects of various policy alternatives on the economy is a far piece from running a business.
In the US faculty senates set some policies, but probably not at the level mentioned in the OP.