Voltage Follower Saturation
From the datasheet you linked to:


  ELECTRICAL CHARACTERISTICS VCC = ±15V, Tamb = +25°C (unless otherwise
  specified)
  
  Vicm : Input Common Mode Voltage Range min +/-11V, typ +15V -12V


Which means that at +/-15V supply, it  is guaranteed to work with the inputs are more than 4V away from either supply, and will usually work from V-(+3V) to V+.

Yours is already doing at least this well...

Now the good news : you can find a drop-in replacement if you search for "rail to rail opamps" which are designed to avoid this limitation. Depending on your application, you can either use one of these, or re-design to use the TL072 within its specifications.