That is really up-to-you. Malwarebytes while it is a useful app is not necessary if you do your due diligence. For example if you don't download anything from web sites you don't know or trust, do not use a Torrent to download apps or other software, ignore pop-up, e-mail, phone calls that threaten you or advise your system has been compromised (they're all SCAMS) your system should remain safe and stable.
If you feel you would be served by using Malwarebytes then it's a good thing to support the developer so he can continue developing it.
I have been a Mac OS User for about 15 years and have NEVER had any need for Malwarebytes, however there are many who have and have been very happy using it.