Someone once asked...
Someone answered with kindness...
It has to do with merit and how you perceive it. Everybody is worth of love. Just remember that. You don't really earn love. You can buy, in some very abstract sense, but earning it, is not what love does (it's a free gift).
Another soul answered...
Because you don't love yourself
Another soul answered...
Childhood trauma.
Another soul answered...
Because your parents loved you conditionally