The basic answer...? - Some people take friendships/connections online a lot more seriously than what some others do, which is where you might find stalking more prominent... For the most part players that just do content and that's all, they may never get stalked (I haven't in the 11 years I've been playing), and then some others may go to social events (or tend to have a more social nature than others), make friends, do RP (Some people also take this more seriously than others), and players like that I would say generally tend to find themselves being stalked more. I've had a few friends where this has been the case.
I also suppose the very existence of this tool/program answers your question as well, because there certainly isn't another reason for it to exist.