Well, someone must need something better than Windows Defender.
The US Treasury says Ransomware payouts in 2021 exceeded $5.2 Billion dollars for a three-year tracking period.
You can have your opinions about when, why, how, etc. but regardless there are still people getting infected daily around the globe that have and use Windows Defender as their main security protection.
Even if you think it will never happen to you (you may be right) it's a possibility and if you don't have your data backed up properly so that the ransomware cannot get to it then you may find your luck simply ran out.
There are underground groups that daily run tools to scan and make sure that no security product can detect their program. Then they sell that in a marketplace arena type operation. Exploits are found all the time and not all of them are reported, they're often used in such attacks until finally they're noticed, and then Microsoft or whoever the attack was directed at fixes the exploit. In the meantime those people that got attacked and did not have good, proper backups lost ALL of their data.
Look at these Black Hat events that go on every year. Microsoft, Macintosh, and Linux all fall to some type of exploit, and the attackers gain root access often within minutes or less and these are on fully protected and up to date systems. Just saying, no box is as protected as you may think it is. The right person or team simply hasn't chosen to target you.