On average? No. It's easier for developers to target only one platform and switching browsers is easy enough for the average user that developers don't see much problem in putting the blame on the browser. Chrome also has greater marketing power backing it than other browsers, so it's the easy choice. That's what happens.

Should you care? I think yes. I don't want the internet to be at the whims of a single entity. It's like authoritarianism vs democracy or having a monopolistic market vs a competitive one. What's best for the tech ecosystem isn't something the average developer thinks or cares about, though. When I show my co-workers how our front-end breaks when using Firefox, they often mistake my concern of portability to be favoritism towards Firefox. I'd use other browsers, but it would just make it harder to convince them to take the bugs seriously.

Sad thing is we fought so hard back in 2006-2009 to get to get past bosses and clients who wanted us to just make it work in IE, and here we are a decade later and those who should be building on our work are tearing it apart by carelessness.

Edit: if any frontend/web developers today reads this, please do use Firefox for development. I'll tell you why:

I can only remember a single time that I wrote something in Firefox that didn't also work in the latest IE, Chrome and Edge.

Web developers I work with who use Chrome however seems to constantly have to go back and fix stuff that doesn't work anywhere but Chrome, exactly like web developers who developed in Frontpage and IE had to.

If you don't want to spend time with regressions from QA and you don't want to look unprofessional, develop on Firefox.

The happy feeling you get from doing something good for the web is a bonus.

I'm full-stack, as they say, but have been working almost exclusively on the back-end for the last couple of years. I don't think I remember a time when I did something in the front-end that resulted in it working in Firefox but not on Chrome, so you might be right, but I may also simply not remember.

I didn't intend it on you personally jolmg, but rather generally frontenders who read it :-)

Will update to make it clear.