Liszt often performed concerts without any sheets and I'm sure he made it a trend amongst pianists.
https://www.rochester.edu/pr/Review/V79N4/0307_liszt.htmlSo if he was performing without sheets why would he look everywhere but never the piano? I'm sure he could have played without looking at all. Looking at your hands while playing has a pleasing aesthetic so why avoid looking at that?
I'm sure with his great skill he could have stared at the ceiling while playing any piece . We don't see any great pianist today never look at their hands unless they are actually blind (which proves that you can indeed play at very high levels without any sight). Also to hear the piano you would often look forward, if you were in a huge hall maybe you'd tilt your head to hear the sound project if necessary.
When sight reading during practice sessions you can still see the piano keyboard and your hands within your peripheral vision and that is useful to stay accurate, it is not as if you see zero of your hands and keys and only the sheets. It is more challenging to sight read when you can't see the keyboard at all, probably why young children find sight sight difficult, usually the sheets for them can be quite high up, their heads angle upwards where adults can be more horizontal, also kids peripheral vision doesn't develop fully until their adult years.