it plays in treble and bass clef
Well they vary between the treble and bass clef. The great thing about the guitar is the variety of notes
A bass clef is used when playing bass guitar because you are plaing bass notes. Because you are using your left hand and not your ritght(treble clef).
Treble cleff for normal 6 string guitar. Bass clef for 4 BASS guitar.
Music for bass guitar is primarily written in bass clef, but parts written higher on the neck can be in tenor clef and G clef.
You can play any instrument with the bass clef. This is just a convention to write notes of certain height in the bass clef. You can play a piece on an instrument if their diapasons match. Or even it is not so, you can transpose a piece to the diapason for your instrument. Usually, pieces written for bass instruments (for example, electric bass guitar or double bass) are noted on the bass clef.
The majority of any score written for bass guitar will use a bass clef. Very rarely will it be anything else.
Because of music theory. The bass guitar is played in the bass clef.
Mostly bass clef, sometimes tenor clef.