My guess..... you are not memorizing the songs, but fake your way through the tune, especially if you are also a singer..

Sure maybe you can remember a hundred songs, maybe a bit more.. but if you take request, a couple hundred songs won't cover it.

Now most pros can work their way through a song, by ear with standard chord changes..

If you are really good at memorizing songs... you will remember the original key and real chord changes...not three chords grin

I would challenge anyone that thinks they memorized more than a hundred songs... I am talking about melody, chords all in the original keys..

At one time ... using fake books , I remembered maybe 300 songs...all standards.. Repeated performing is the key..

I do believe I had a photographic mind years ago.. I could remember the location in the fake books, even page numbers...

Even today, I play standards in the original keys.. Habits are hard to break smile