Insulation of an unheated workshop
Well..

1) If it's not in the way and not hurting anything, then removing it seems like unnecessary work. Besides the initial removal, there's disposal.

2) It provides some sound dampening...shop work can be loud and your neighbors may appreciate it as-is.

3) Where there's at least a 110v/15amp outlet, there can be a temporary space heater, and so that insulation could potentially provide some benefits in that respect.

My opinion: Keep it.