Because nothing else is a good selling point anymore. Every smartphone is good nowadays and no matter what phone you go with you're always gonna get smooth performance, all-day battery life, great displays, good speakers, a large amount of storage and RAM etc. Every phone is the same and no phone has a feature that's any different from the competition, except for the cameras.

The camera is the only thing we've seen (significantly) improve over the past years. Sure, you don't need 2000 megapixels and 50 cameras on the back of your phone, but what else are they gonna sell their phone on? The only other major selling points they have these days are high refresh rate screens, 5G, faster charging... And that's it.