Legit question. I understand they're useful for roughly grouping together common themes and the environment in which different groups were facing, but some of the heated arguments I see are just like... why do you care so much? Why is it worth 20 pages to argue about whether Brave Girls is technically second or third gen? Why does it matter at what specific point in 2018 fourth gen started, so does ATEEZ count as fourth gen while (G)I-DLE is third?
There's a weird intensity about it that I don't follow. It kind of reminds me of how people want to be like "well, technically I'm a Millennial but I'm more Gen Z." No you aren't, stfu. It's literally just lumping people together based on birth dates; it's not a deep personality analysis.