We have exploits and drive by viruses that can be triggered by just visiting a website. Personally, I use free Bitdefender and free Malwarebytes Anti-exploit. A friend uses the paid Bitdefender and HitmanPro.Alert. He's frequently gone into areas I wouldn't even dare go and he's never had to reformat, etc.
Biggest takeaway... KEEP your browsers, operating system, and antivirus/anti-malware progs completely updated. If you don't, you can easily get infected. So I cannot say it enough.. keep them up-to-date. Another thing I do is keep all programs updated - even games.
I've been running Win 10 for 2 years and never reformatted. Had windows 7 for 2 years prior without any reformatting, viruses, etc. Now, I did have accounts hacked but that was only because I had federal work and the chinese hacked my employer's database and the yahoo hack got me, too. Now I've got this frickin notepad full of passwords, etc. I mean written notepad in my own encryption.