[1] https://www.bloomberg.com/opinion/articles/2022-05-04/cheeri...
1. Stronger filaments that last longer will be a lot less efficient, so the consumer ends up using a lot more electricity.
2. The filament doesn't burn per-say, but actually evaporates. This is why it'll eventually break. But where does the evaporated metal go? It condenses on the inner surface of the glass, making the lightbulb dimmer than when it was new.
So 1000 hours is a good middle ground. The lightbulb is fairly efficient and 1000 hours isn't long enough for the inside of the glass to get too dark from the condensed filament metal.
Price of the bulbs was also reasonably low. It's cheaper to change out a lightbulb every 1000 hours than the electricity costs of a 10 000 hour lightbulb that emits the same amount of visible light. I don't have hard numbers for that, but it's my understanding.
Watch the youtube video linked by one of the grandparent comments. It's super informative and also contains some experiments to show the trade-offs.
Ultimately which scenario makes the most sense: that these businesses went through the time and effort to set up this testing organization out of a desire to ensure they all made better products for consumers, or out of a realization that they could all stabilize their revenues if they all sold products that would need to be replaced on a regular basis?
This also strikes me as an area where consumer choice can be particularly effective: most of the attributes of a lightbulb aside from energy consumption are pretty tangible to the end user, and since they are fairly inexpensive and replaceable, the buyer is more able to evaluate them side by side than many other things. It makes total sense to me that the manufacturers would see this as a problem, and choose to limit consumer choice instead of competing to make better products.