1. the bricks don't have studs. the texture on top implies them, but they aren't there.
2. blockheads are so small that it's like the equivalent of walking on any surface. walking up a staircase doesn't hurt, but it might if you were a giant because your foot hits all the edges of the steps.
3. blockheads are inanimate/don't have nerve endings in their feet
4. their feet aren't even attached to their bodies so even if they did have nerves, the synapse would be huge