Every automatic transmission car I've driven (not sure if all do this) allow you to shift from Reverse to Neutral and from Neutral to Drive (and therefore Reverse all the way to Drive) without pressing the brake or hitting the little shift lock on the gear selector. However, it doesn't let you go the opposite direction from Drive to Reverse, or Reverse to Park, etc.
According to this question if you don't stop completely before shifting its possible to damage your transmission. Some cars apparently mitigate this damage but it still seems strange to even allow the opportunity.
So why would car designers give you the feature to shift from reverse to drive without hitting the brake of it can cause damage? Even if it didn't cause damage why would they not allow you to shift in the reverse order without braking?
Please note I'm not asking how this is done, I'm asking why it is like this.