Gengis, you are of course correct. We don't need to take off.
But sometimes we take off and then have an unexpected (despite full preparation and best planning) change in the weather or a mechanical problem. I well remember a flight from inland France to Calais with a sudden and unexpected change in the weather which led to us moving our flightpath offshore as there was less to hit at the low altitude forced on us in a vfr aircraft. So, yes I was at 600 feet over the beach, with the airport as the best option and the beach as a backup. A 180 turn was not an option, that was closing in faster than in front....as the engine kept turning all was eventually well and we landed at Calais and spent the night there.
Forecasting is still a black art. This was in the days when one could talk to the met man, who had advised us that the incoming frontal system would not arrive before late evening. By 15.00 we got thoroughly caught out as the crud formed around us.
I had a similar experience last week dodging round rain showers, until I could dodge no more as a wall of black cloud blocked my way. That resulted in a scurry back to my departure field and some more waiting as the muck came through.
Sh*t happens, and whilst we should be able to avoid such situations sometimes we do get into difficult corners.
It's an interesting thread, but some of the people posting here are a good deal more altruistic than seems feasible. I don't know if I would be thinking that clearly in the circumstances described, I suspect self preservation would be operating on all four cylinders.
What was it about starting with a full bag of luck and an empty bag of experience? How many of us have about half a bag of each by now?