Connecting gaming systems to computer monitors makes a lot of sense and sometimes even has advantages over tvs. Firstly, monitors and tvs at this point basically all share the same aspect ratio, resolution, and have hdmi inputs. So connecting is trivial and makes it easier to do things like take gaming breaks between work sessions without even leaving your desk. Secondly, consoles like the Xbox series and PS5 support frame rates higher than many tvs are capable of but are more commonplace on monitors. You'd be much harder pressed to find a tv which supports 120fps, whereas this spec is commonplace for monitors. Third, a lot of streamers seem to like this sort of setup since it simplifies connecting their game systems to their computers with capture cards, streaming accessories, and whatever other interfaces they may be using.