The free version of Malwarebytes does not have real time protection. This is a good thing if you are already using an AV that has real time protection. Yes, you can buy the premium version of Malwarebytes and disable the real time protection (so it won't interfere with your primary AV), but I guess I don't see the advantage of doing this (over just using the free version). The free version of Malwarebytes has to be manually updated, but I don't think that is that much trouble.
I run the free version of Malwarebytes on my laptop as a secondary scanner, with Norton as my primary AV. (Norton came with the new laptop, and it would be more trouble to uninstall it to put in another AV program).