Why does hunger have a much more drastic effect in cycling than in other endurance activities? When I'm out cycling I know that once I feel hungry, I only have around half an hour to refuel, otherwise I will bonk in a way that all performance is lost and it feels as if the only way to get me home is by pure will. This seems to be a rather common phenomenon since among German speaking riders there is even a name ("Hungerast") for this state. On the other hand I can go out for a 1-hour-plus run at similar intensity while already being hungry without bonking and even am able to push it hard at the one or other uphill during the run. Even if I push this quite far it does not feel as bad as in cycling but only gets more or less an "annoying" feeling that my thoughts start to revolve more around being hungry.

Does anyone have an explanation why this does feel so different in these two activities?
The short answer is that it is purely down to your individual training level and mechanical efficiency in each of these disciplines.

Bonking is a result of fully depleting your glycogen stores.  Once this occurs, your body's only source of fuel to power your exercise is to metabolise fat.  This does not change regardless of what activity you are performing.

However, your state of training and efficiency can impact how long your remaining glycogen stores can last.

As an example, consider the case where an athlete is significantly less trained at running, than cycling.  In this case the perceived effort level may be the same, but in fact, when running, the muscles are generating less power, hence requiring less fuel, and allowing them to last longer before bonking.