This excites them and they share it under the assumption someone else has their exact needs but lacks the inclination to have AI make one of their own.
The real question is why does HN keep upvoting them?
Because a significantly large demographic of HN is aggressively pro-AI to the point of cultishness and the mere existence of such applications, to them, is a vindication of all of their beliefs and an expression of triumph over all of the critics and doubters.
Note that it doesn't actually matter how well they work, or whether they work at all. Many people will assume by default that they do, and that anyone claiming otherwise is just a deluded, bitter Luddite, and will praise and defend them regardless of quality. The rules and standards that apply to human written software don't apply to AI generated software.
I do however think sharing your own personal vibecoded software is a bit like saying "hey world! Check out how good the plot is on the latest page of my diary!"
The problem is many AI developers don't want to have to care about the code, or human expertise. They consider the process beneath them. They want to trust the LLM implicitly, believing in its superior intelligence. They want to already be living in the sci-fi post scarcity post singularity universe where they can just say "Computer make me a photoshop" and it just happens, perfectly and without error. And all else being equal... that attitude will never lead to quality software, it will only lead to vibecoded slop.
It's sad because there are already plenty of open source alternatives to Adobe[0], but none of them are AI generated, so no one is going to bother trying to support or contribute to them. Except with vibe-coded slop PRs.
That is to say, maybe they'd put down for something professional for a special occasion, but the one they can make with the thing in their pocket is good enough 99% of the time.
The world where that's possible with photographs has been here for over a decade, but with software it has only arrived this past year. So it's novel. I guess I've answered my own question about why it gets upvoted. I still hate seeing it. I wonder if something similar happened when digital cameras first got cheap.