Which "modern rock musicians" do that? It surely is not widespread in rock.
Rock musicians change guitars (in a live or even studio situation) mostly to get a different sound or a different tuning (like going from "standard" to an open tuning). Not for microtuning adjustments, or because they have moved the frets to match an individual piece.
Some prog musicians might do it, but it surely is not a "rock" custom.
In arabic music, on the other hand, or renaissance music, and other genres, it is, and instruments there often have movable frets.
Rock musicians change guitars (in a live or even studio situation) mostly to get a different sound or a different tuning (like going from "standard" to an open tuning). Not for microtuning adjustments, or because they have moved the frets to match an individual piece.
Some prog musicians might do it, but it surely is not a "rock" custom.
In arabic music, on the other hand, or renaissance music, and other genres, it is, and instruments there often have movable frets.