Been doing a lot of flat water pumping during the lockdown and I can now say without any doubt that for flat water pumping I definitely prefer no straps. Like Gunnar said, straps lead to poor technique, and weirdly, using straps seems to reduce my stability when flat water pumping rather than increase it

HOWEVER, for SUP foiling and wing foiling I still like to use a front foot strap for the following reasons:
 - Extra traction when taking off (especially necessary for me when downwinding or trying to catch super small waves).
 - When losing power from a wave or swell - just to help lift the nose before it touches the water.
 - When cranking turns on a wave!!!!!!!!!!

I'm sure as I get better I'll need them less and less, but I don't think there's anything wrong with using them to learn - as long as you don't get reliant on them.