And hence the EX part! I totally get that... I left one like that behind, a long time ago, as well. Far too much drah-mah!

I suppose it varies from person to person, although in many cases they were raised in families that either TOTALLY ignored them (overcompensation) or TOTALLY coddled them (learned behavior). In the case of my distant ex, she had "learned" that the only way to get significant attention in a larger family was to be SICK. So she always had "ailments" to get people to rally around her....

But yes, there may be an element of selfishness, too. It's one thing that they manipulate situations... but WHY did they get to believe they get to be the center of the universe?