It can be the effort, it can be the dedication which you must show, and anything else like that. But forming a relationship could mean a lot - especially if you have a variety of interests in common.
I constantly remember moments where I've wished I'd had someone to talk to, as I myself would try my best to listen and encourage any people to talk - but the problem was that I would just end up as their 'talking buddies'. They would talk on, as if it was some monologue, and I would constantly nod and listen. But whatever that I wished to communicate back, would only be 'heard', i.e, not 'listened'.
In the case above, I really wanted to have a good friend, because I really wanted to talk about something to them - it was exciting to talk about stuff with someone, if I knew the person was pretty much like me.
Maybe you did not think it interesting for so many years, that you should have given it a try - maybe you were doing pretty well by yourself. In that case, I can relate to you as well, as I really like to be left alone most of the time. I even have to admit that there is some sort of 'joy' in just being a totally isolated guy.
But then again, what are your needs from a partner, in the case of a relationship?
What are your expectations? Would you have too many of that? Would you be happy with someone who appreciated your company?
Or, you could have been getting a lot of satisfaction from the many things which you were doing in life? That could have led you to completely 'forget' and 'move on' to other things in life.