Lots of people feel it's vain or egotistical to praise themselves.
Some people even have a hard time accepting complements!
Example: "Ricki, That's a beautiful dress." (Reply) "This old thing?"
They simply can't say: "Thank you."
This probably explains why so many books written on the topic of "self love", building self-esteem, learning to love yourself...etc are bestsellers!
Another sad fact is a lot of people during their "formative years" of childhood were never praised by their own parents. If your own parents don't make you feel "special" it's going to take a lot of work to convince yourself you are. It's even worse if you weren't accepted by other children at school and other social gatherings.
"The Greatest Love of All is Learning to Love Yourself."