we all crave attention; women want attention just as much as men do; we all want to feel loved and wanted and needed and cherished.
Because they're human? People value and need apreciation, some more than others
Because their other halves / partners don't offer it!
Those that do are insecure. Insecurity usually stems from lack of parental attention. Attention makes them feel special. Not all women are like that, surely you see a lot of men like that.
Just another of those annoying habits we have so many of.