A good website that demonstrates some ability to write frontend code well is a shortcut to demonstrating that you're good at what I want to employ you to do. It's a showcase of your skills, just as a graphic designer would have a Dribbble portfolio or a backend dev would have a few repos on Github. I'm not suggesting you can't get hired without a nice site, but if I get your resume you're much more likely to get a call for an interview if you do.
No, the equivalent here would be to expect back-end devs to build their own blog applications. What a waste of time. I did that when I was younger and it was only a distraction from actually writing and building things that mattered.
However, outside of junior level positions, I don't think there's much you can glean from whether somebody has done trivial side projects or not. Obviously an ambitious side project is worth a lot, but the bar for building one is really high and there are so many great devs who can't reasonably make the time outside of work to do that.
No one is forcing you to do any of this stuff. If you can find a job you like without doing it then that's awesome, but plenty of people can't. I'm suggesting a way that people can avoid being filtered out based on their resume because, whether you like it or not, wanting a candidate to demonstrate that they can code reasonably well before the interview stage is quite common.
I think people get a bit too hung up on the way FAANG-size corporations do hiring, with code tests, full time hiring managers, etc. That's only a fraction of the software industry, and if you're applying to somewhere smaller having a public portfolio is useful.
That you should build something if you don't have anything to show off at all is a completely different point -- and that doesn't seem to be your point when I reread your previous comment? At which point, I'd recommend building something more interesting than a blog unless you're a beginner, and I'd avoid mixing your writing with your attempt to build your first demo project. But this thread isn't about beginner advice.
(I say this as someone who used to overengineer my own personal websites with the hottest tech stack of the week, but am now in the process of throwing it all away for a simple WordPress site.)