On/Off led

That is true Tricky. For issues like LEDs and human-finger triggered switches and similar starters' projects, I don't see any need for clock edge to sample changes. However it is useful to use correct methods at least to keep the professor happy.

Apart from that I might also use a slow clock to debounce the tremor of old fat fingers.

The benefit of not using clock is that you don't need to care about the fuss of TimeQuest reporting failures on registers.