Why people dont leave likes?

The title explain it self, i mean, i have already almost 60+ post and its very strange see a like in post/threads.
So my question is: why people dont leave ever a like? its so simple click that little heart, why would you wont do it men?
If you dont have the answer to my question answer this or both: why do you dont leave likes normaly?

that's all what i want to say. Peace