Fabric under the foot provides a cushion between the foot and the feed dogs, similar to the cushions in the bottom of your feet. Can you imagine the wear your bones would take on gravel without them?
The dealer I bought my first Pfaff from years ago told me to leave the machine with the foot down as it's better for the tension disks.
I left the needle down until the time I forgot to bring it up before turning the machine on. It really knocked the machine out of time and broke the needle and a machine part. Now I always leave the needle up, even though my new machine raises the needle when the power comes on.