I guess because I don't care about face ID. It's more of a gimick, and raises privacy concerns for me. A cop can unlock your phone without your consent, by pointing it at your face. He can't force you to enter a PIN or trace a pattern...
Apart from that, while it seems to work fine for me, so did Samsungs face and retina ID. The Essential had the first edge to edge screen with a bezel as small as the XS, last year, and have a tiny notch. I found that to be a nice balance, personally. The phone was smaller than the iPhone 8, but managed to have a screen larger than the 8+. The fingerprint scanner on the back was among the fastest out there, and your finger went right to it when you picked up the phone, naturally.
I would rather have a thin bezel on top to house face id stuff, than to lose a significant portion of my usable screen area. It's not really a 6.1" screen, when you lose a quarter of an inch from the top...
Maybe if Apple comes out with sensors that work underneath the display, they would be cool. Similar to how OnePlus and others are not offering fingerprint scanners on the screen, so you don't have to see it or have a bezel...