There's not much left to "fix" on mobile phones, and no real important features to add. Lacking that, they need something to sell the phones with, so they're going for these strange "improvements". It needs to be something that has some wow factor so they can lead with. This seems to somehow work on normal people so they'll keep doing these "improvements".
I expect in the future they'll pull this trick again, moving bits of the phone upwards towards camera, and create a second notch from half way down, where the phone will get even thinner, and they'll sell that.