Well i have personally never seen any good concert pianists play with sheet music. I see accompanists with sheets yes, but never ever solo peformance with sheet. I think music has to be absorbed, then it literally becomes a part of you. It is stored somewhere inside the brain of ours. When it becomes organic then it develops freely through your creativity. When you have sheet music as ur security blanket, or guide even, you are neglecting full focus on sound production since there is that concerned about what the notes are actually doing on the page.
One of my piano teachers could read 8+ bars ahead of herself, turn pages before she even finished playing it, even if she never heard the piece before. I remember even writing music on a scrap peice of paper and asked her to play it and she could! And my writing is hell messy lol. That amount of sightreading skill is amazing and extremely useful. You cannot disregard the power that has. She was very much in demand for accompanying which in itself can earn you a good living.
For me, throw something i never seen and ill play it 20%or less tempo but when ive finished ill remember a lot what i played. Burn the sheet music and i still would have some idea what to do, but a sight reader? You always need your sheet music, you have to say to people who ask you to play, oh sorry I dont have the sheet music. I usually use that excuse if i cant play the piece

!!!! But relying on sheet to play would would frustrate the hell out of me.
Even though im still young (23) i find that the connection between what you hear from within to what you produce at the piano gets stronger and stronger. I have only ever been a memoriser, my sight reading skills are average, but no way i could sightread Liszt, or crazy chords of Ravel, Scriabin etc at tempo like some can. But if i listen to Cd long enough, i can reproduce what i hear. This skill is so much more useful and faster than sightreading in my opinion.
When you have listened to a piece for a while you can probably hear it playing inside you without listening to the recording. But when it comes to playing it, that is a different story. You can hear from within what it should sound like, but the fingers play the wrong notes if they try. Your ear can tell that it is wrong, but your fingers do not know where to go to correct it. BUT what i am saying is that this process, of playing by the ear can develop and gets stronger. I can usually play peices i havent ever played before just by listening to it played a few times. The parts i miss have to be read but this reduces the amount of music i actually have to read. That makes my reading work not very hard at all, and I can skip over bars which i "guess" is right through the sound from within. Of course you go back and check if what you think is right is actually right.
I have only ever worked like this my whole life. Personally, sheet music becoming more and more useless because of it.
And if you really think about it, sheet music was only created a few hundred years ago. It isn't the best way to learn music, the best way to learn music is to play whatever you hear from within, how on earth do you develop that. I can only say do it, there are many courses which teach you how to play by ear but reckon the only way is to do it day in day out. i use to do it when i was a younger kid, i couldn't go uot and buy the sheet music for lots of music so i just listened to the Cassette tapes and pressed stop, play stop play, rewind, stop play rewind ahahah. thousands of times until i played what was being played back to me.
Music to me is about playing with just yourself and the instrument. Whatever lies inbetween that (sheetmusic) just limits the connection and enjoyment.