The space being wider and the spaces being close to the door are two separate accommodations. Leaving it gravel leaves one solved (distance) and simply avoids the other (width) completely while ignoring that caused a 3rd (gravel if you do manage to get out). The guaranteed width is so there is a standard amount of space to exit the vehicle, see the drawing at https://www.ada.gov/restriping_parking/restriping2015.html

But yes it gets increasingly hard to have a good solution for everyone when there are so few spaces.