I have those electronic materials. They come in two varieties. There's something called iRealB, which contains thousands of tunes, but is just chord changes due to a quirk of copyright law -- the melody and lyrics are copyrighted but not the harmony. That's the one where you can transpose tunes. But you don't get the melody.

Then there are large PDFs where somebody ran the old paper fake books through a scanner, but they are just images and are not in an actual computer readable format, so they can't be transposed.

So the computer has not solved the notation problem, yet.

Myself, I've memorized most of the standard jazz repertoire.

In fact I suspect that most of the written music repertoire that exists today will never be translated into computer readable form, because it's just too much work. And not enough new music is being composed to form a critical mass around some new notation system or computer format. When somebody composes a tune (I play in one band that does original jazz compositions), they send out a PDF.

Maybe software will eventually automate the process reliably enough to be useful.