Windows does have Defender, which does some amount of tracking signatures and heuristics of various types of malware.
It has not, however, proved enough to fend off different real world problems like ransomware.
Hence, the market for 3rd party solutions that are more aggressive. And to keep up with real world threats, they have to update often. And have to run at high privilege levels. So now you have the situation where those third-party solutions have the ability to create a bsod and/or a boot loop. Which should mean that they have a very well thought out way to roll out updates.
Very much every 3rd party anti-virus software I tried (and paid for) caused data loss or other problems (a few catastrophic) in the long run. One product didn't even stop a virus getting in.
Since then I just use Defender and never had any trouble or a virus or ransomware. Only issue is that sometimes the antimalware service takes a lot of CPU.
Microsoft has a high share in this area but enterprise security is generally a very competivite market. Microsoft may even move into #1 position as a fallout from this debacle becasue the market share between them and the #1 CS is very small (that does not mean people actually buy more Ms btw... if that needs to be said ;)
This is not neccesarily a good thing for MSFT as it will 100% trigger regulator rage in the EU.
It has not, however, proved enough to fend off different real world problems like ransomware.
Hence, the market for 3rd party solutions that are more aggressive. And to keep up with real world threats, they have to update often. And have to run at high privilege levels. So now you have the situation where those third-party solutions have the ability to create a bsod and/or a boot loop. Which should mean that they have a very well thought out way to roll out updates.