Because it (a) works great for users, (b) is the most secure (check reported vulnerabilities) (c) by far the best at fixing reported bugs in my experience, and (d) is by far the best for development for me.
Safari, Firefox and Edge are failing to win on the shit that matters, and as a web developer all three competitors make my life bad.
And we learned nothing from the IE era? The problem with IE wasn't only that it was bad, that was the cherry on the shitpile, the real problem was that it had 90% marketshare and websites simply would not work with anything else.
In re: to your points
A) doesn't work great for me, there isn't even an integrated side view or screenshot addon, not even mentioning the lack of integrated tracking blocker
B) lower number of reported vulnerabilities != most secure, this should be fairly obvious if you ever worked with netsec and websec people
C) I heavily disagree, chrome developers simply ignore bug reports if the resolution doesn't fit into their agenda. If your site doesn't work on chrome, you either suck it up and make it work or be prepared for chrome devs to ignore you unless you're big enough for them to care.
D) For you maybe, rest of the world? maybe. The Firefox Dev console has been utterly sufficient for my use cases in webdev.
You should intensely care about Edge, Firefox and maybe even Safari failing to win because if they do loose then you're going to be part of the group that will be responsible for the next IEficiation of the internet.
Because it (a) works great for users, (b) is the most secure (check reported vulnerabilities) (c) by far the best at fixing reported bugs in my experience, and (d) is by far the best for development for me.
Safari, Firefox and Edge are failing to win on the shit that matters, and as a web developer all three competitors make my life bad.