This malware magnet hasn't had an infection in well over 8 years, coincidence that I have had avast for over 8 years.
But you have had to be saved by avast! from attacks on your system.
Windows is the main target not just because of sheer numbers of systems but because it is flawed and so easily taken down. If Windows forced users to only run in Limited User mode the vast majority of malware would be dead in the water. Malware propogates because of poor/sloppy user standards, you are more astute and avoid the problems but look at all the extra armour users are having to put on, read the signatures here on this forum and see the ridiculous number of security apps people are using in an attempt to stay safe.
I have had no infections on any system here for years but that is down to forethought and planning and preventing malware sites connecting to my router more than the apps I run on these machines.
Change to Linux and I have zero need for any of these things and there is no disc cleaning,defragging, endless checking ,resetting and improving the system, I just boot up and use my machines for their intended purpose.
The reason Unix,Linux BSD and OSx are not tagetted often is not down to numbers of systems, there are millions of users and servers out there, it is because it is a lot harder to write anything that will propogate on those systems. There is no registry to infect and the systems don't run in "root" , that is why if you look at the antivirus apps they basically check for Windows infections in email and files so they don't get passed on. Bottom line is the numbers of machines are there but the payoff for trying to write the malware code is going to be next to zero so the malware writers are going to find other targets.