alt Hacker NewsA little bit (scolding a beginner in this way is never acceptable), but I do feel like the 555 is really overrepresented in electronics learning materials. It's a quirky little chip, so learning about it doesn't really teach you much (most of the time it's just 'hook it up like so and it does this!', not 'here's how comparators and oscillators actually work'), and it's also now almost never the best or even a good solution for any of the problems it solves.
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It's true. They're not useful for anything not hooked up to mains.
I was meaning to add footstep-activated lights to my stairs using vibration sensors and 555 timers, but then I learned that if I tried to operate them from a battery, the 555 would drain it in hours, while a much more sophisticated ESP32-c3, would last a month in sleep mode on two coin batteries or one li-ion in the same form factor all while being part of a development board that greatly increases idle current.
That's true but because it is a quirky useful little chip it is for many people their first exposure to integrated circuits that are a bit more 'analog' than gates and micro controllers. Opamps are the other gateway drug I guess.
It's excellent teaching material for that reason alone, you do learn about it if you try to understand what makes it tick (there are plenty of articles about it, including blown up versions). I agree it is not the best solution for most applications but I'm happy to admit that I've actually used it in production designs (more than once, actually) where it made good sense to have a component that didn't have to be programmed. If you have a soft component on a board and a spare io line then you are usually better off doing it in some different way.
I've seen some interesting applications of 555s that would have taken a lot more hardware otherwise, one of which was an oven controller with used a thermistor to directly affect the PWM output of a 555.