As you may be aware, the mud is much easier to remove when it is still wet, so the faster you get it done after your ride the less effort required and the more thorough a cleaning job can be.
Two situations that occur to me are the following, but I'm sure there are more:
- My outdoor hosebibs are located such that I shut down and drain the exterior water line to the hosebibs for the winter. However, that does not stop me from riding and so I often find myself with a muddy bike and no means to wash it.
- Sometimes I will drive (by vehicle) to a remote location and encounter sufficiently muddy trails. There is no place to wash the bike, so you load it back on your vehicle and the mud dries on the way home. This assumes there is no creek nearby to wash your bike in.