So? I see no problem with that whatsoever. As far as I'm concerned anybody should be allowed to buy anything from anyone else so long as they're willing to sell it (and its main purpose isn't to harm others, eg. weapons). I do think there should be state run businesses in any vital industries, but not only are cinemas not vital, even if they were that still wouldn't make a difference here.
Sure, I'm biased in that I think cinemas offer a massively inferior viewing experience to TV and are insanely overpriced, but you're biased the other way so you can't really call me out for that.
I can point out one HUGE problem with studios owning theaters, Securities Fraud.
Right now, theaters get none of the box office revenue for the first two weekends. That horrible deal allows studios to buy up tickets to inflate the performance of certain movies. So, a massive flop can be converted into a modest success thereby affecting the stock price of the parent company. Hollywood accounting is already extremely corrupt, this would take it to a whole new level.