I am massively emotionally invested and wish I wasn't. I find that the PhD work is far more interesting than a lot of other activities, so just become overly dependent on my work for gratification. I think that is the mentality of a lot of researchers, were we are paid to become obsessed over a specific area. Why worry about reality TV or large friendship groups when we can try and solve an interesting problem. It usually turns into me having an existential crisis while making a conference poster at 11pm but again it is far more interesting than playing FIFA (which I used to love). I think a major difference is that I enjoy thinking, I don't want to sit down and turn off, while academia/research is a huge source of thought provoking research
What I am trying to say is academia attracts a certain type of person that likes being mentally stimulated, in my opinion. And therefore we treat our PhDs like a drug and are addicted, in my opinion. If the rest of the world was just as interesting we would be fine.