As a guitar player, I can tell you that I used to spend a lot of time re-tuning to learn songs off records. Sometimes the tuning changed from song to song on the same album - which is why I never got used to using a tuner.
Unless brass or keys were involved, the tuning on many rock albums used to be anything but standard 440. And of course, some musicians voluntarily strayed from 440 for entire records (Black Sabbath Volume 4 comes to mind). Stevie Ray Vaughan and many other guitarists favoured tuning down a half step too.
As such, I personally never paid much attention to tuning up to standard until recent years. In fact, I've be re-working an old song for which my guitar was tuned extremely low (2 tones down IIRC). That particular song has piano in it, but it makes no differences so long as you are spot on on whichever note you decide to tune to.