A few reasons here buddy, let's dive into them.
Kendrick approaches things from more dynamic approach. Look at Good Kid M.A.A.D City. Kendrick is rapping about the societal pressures that cause people to do things such as drugs and gang-bang. Kendrick not only has lived through the issues he is speaking on, but has done his research on them and dives into them from multiple view points.
Hopsin on the other hand just points at people and says, "wow, you do X, you're such shit and throwing your life away!" He has this holier-than-thou approach to his songs. Not only that, but his observations on social issues are painfully obvious to the point they are laughable. He's not bringing perspective like Kendrick is. Listen to this remix of Ill Mind 5 to see what I'm talking about
Hopsin also goes around dissing any new rapper because they're "fake." Shit, he dissed Kendrick
Just beacuase your rap about social issues doesn't make your music "real" or "intellectual"
Here are some other thoughts and opinions on this man
By far the best explination here. Anthony Fantano hits the problem with Hopsin so hard.
https://www.reddit.com/r/OutOfTheLo..._does_rhiphopheads_hate_the_rapper_hopsin_so/