Does leave fawns nestled down in high grass or forest hollows while they scout an area. The fawns will not move at all until the doe returns. You can walk right up and touch them (but you might get a painful surprise if the doe returns without warning). It's a survival strategy that works for the deer - as somebody pointed out, their number are increasing - because the fawn's unlikely to be able to outrun a predator or be able to navigate effectively without its mother. It's best bet is absolute motionlessness, because most deer predators will home in on motion.
Sometimes the doe will get run off in some other direction while scouting, and won't come back for a day or more. The fawn will not move until a doe finds it, but I don't think it has to be the actual mother, any doe will probably do.
As several insightful people have pointed out, the hazard is not all for the deer. Running over a fawn with a combine can't be good for the machinery or for the crop, a cheap drone could be a worthwhile investment.