I had a coworker who thought she had a blurred background on when she joined a meeting and her room was fucking filthy. She saw her background wasn't blurred and was very embarrassed.
Anytime I see that it makes it obvious the person is trying to hide something. I assume you're a slob if you do that. Or ridiculously paranoid(considering you're already showing your face).
It says you know it's disgusting and embarrassing AND you are willing to live like that. The only effort you will take to solving it is throwing a digital sheet over it.
Or maybe someone just thinks it looks good and would rather not show their bedroom to the entire conference...? And that's a problem... Why? Because you think the inside of their bedroom is everyone's business and they're mentally unwell for being more comfortable with a blurred background?
Please refrain from sharing your opinions when the only contents thereof are hate towards another individual for something which helps that individual feel more comfortable while effecting absolutely no one in any way whatsoever...
Like someone else said, the edges break through. We can tell a light blur to obfuscate your tidy room from a complete screen change that breaks occasionally, revealing your mess. It's not that well hidden.
I always have a custom background on even though my room is tidy. It's just that our bed is directly behind me and I don't particularly feel like showing everyone our bed, even though really it's harmless. It's just a privacy thing, not something to hide mess.