TLDW: The Phoebus Cartel established 1000 hours as a baseline to get maximum efficiency. longer lasting bulbs would require WAY more power per hour to operate while producing less light.
Planned obsolescence is indeed a thing, but using this as an example of it is incorrect and discredits the overall argument. It’s better to focus your attention on right-to-repair laws for your $2000 laptops and $40,000 tractors than on your $2 light bulbs.
I’d absolutely recommend watching Alec’s video, but that’s not a half-bad summary of the main point.
Think about it hard enough and it does make sense that for something as cheap and easy to produce as a light bulb, it stands that the consumer and manufacturers alike stand to benefit from a shorter, but more energy/cost efficient implementation, than a longer-lived, but significantly less efficient/more costly version in general use.
Edit - Though it should be pointed out that this is a rare instance of corporate interests lining up with the best interests of the majority of consumers, not something that happens very often, so you could see why people (even myself) would be drawn to believing a more nefarious reason for the 1000 hour lifespan if you didn’t know the technical details.