Whenever I sit down at the piano and just improvise over chords or just make up stuff, time goes by way faster than when I sit down and practice a piece of musi

Whenever I sit down at the piano and just improvise over chords or just make up stuff, time goes by way faster than when I sit down and practice a piece of music. Though, time also goes way faster when I am sight reading new pieces than when I am practicing, so I am not sure if it just because I hate practicing a specific piece and time is slower when I hate doing something or what.