It's because they don't trust Americans to angle your seat correctly.
One of the very few deaths in a smart car was because he had reclined his seat too far and he got shunted from behind, his head got caught between the headrest and the roof and broke his neck.
A lot of the silly designs are because they don't trust Americans, head pads, seat belt noises, partially reclining seats. We don't get any of that in Europe.
Infact, the door locks had to be changed incase an American (which for their tests was calculated as twice the weight of the european test) didn't close the door properly so it was just on the latch, wasn't wearing a seatbelt, went round a tight corner and leaned on the door. They had to make sure it was gonna hold.
If you take the seat off its runners (remember to disconnect the battery) you will probably find 2 metal tabs that limit movement, gring them off.