I put Malwarebytes on my computer.  It's a full version but a trial version.  It monitors in real time, all the time.  I've run AVG and Windows Defender on the computer and never had any problems.

I ran Malwarebytes and it found nothing on the computer when I installed it.  I ran it a couple more times in the next few days, it never found anything.

Then I booted into safe mode and ran Malwarebytes and it found 1 piece of malware.

So, why should I buy Malwarebytes for it's ability catch malware and for its ability to preform a scan at startup to remove malware it doesn't stop malware and doesn't find it when operating the computer normally? 

It only found it when I booted into safe mode.  Not something I am want to do on a regular basis and not something most people do or even know how to do.