I had two Samsung flagship phones, one (S20FE) had an optical fingerprint reader and the other (S22) had an ultrasonic one. Both of them somewhat regularly failed to read my finger, were slower than a fingerprint reader on the power button and are more expensive/complex to build. They won’t work with cheap 3rd party screen replacements and some screen protectors as well.
Meanwhile my $90 Android phone has a fingerprint reader on the power button. It never fails and I never have to perfectly place my finger on the sensor area to get it to work. It just seems like the perfect place to put a fingerprint sensor, so why do phone manufacturers keep using in-display fingerprint readers over the cheaper alternative?
I loved the Pixel 4 I had with the reader on the back. My finger was already there when I picked up the phone, and it was way more accurate than the one on the screen of my 6.
Miss that phone, except for the nightmare charging port.
You could also swipe down on the reader to bring down the notification tray, I miss that fingerprint reader every day.