Reasons to hate Copyleft license
Copyleft license stated that any code that incorporated works under copyleft license (“derived work”) need to be licensed under same license. Their purpose is to make everyone contribute back to community, as in “Free as in Freedom” phrase by RMS. This idea look very good, and is in fact a very good idea to promote free and open source software.
But people do need to eat, drink have needs. They also need money to survive.