One thing I've discovered about the piano transcriptions I've used is that the key is usually "guitar friendly". Guitarists and pianists have different keys they prefer, mostly because those chords are the easiest to play on their instruments. Guitarists usually like to play in the key of E or A or D, since guitars are naturally tuned to those chords. Pianists like to play in the key of C or F or Bb, since those chords are easier to form on the piano keys.
Whenever I get a piano transcription, it's almost always written in the original key of the recorded version or in those keys favored by guitarists. I don't mind it, because I know how hard it is for guitarists to play chords like C major and F major. I can always adjust my fingering to play in E or A or D, but other instruments may not be able to transpose keys like that.