I do try to wash before using but it doesn't always happen. One reason I wash first is to reduce bleed. Nothing worse than to have a quilt ruined when it is washed when finished due to a colour bleed even with colour catchers in the machine.
A final wash before giving makes the quilt go puffy. I don't wash baby quilts I give them to mum to use her washing powder. I come from a family allergic to certain brands so would hate a baby have the same problem