The gent forgets planes divert for safety and it is far better than it used to be, when every 747/DC-10/Tristar had to divert when the RVR dropped to 550m then 300m.
Now its 075m RVR most Boeings and 125m on Airbus..although stand to be corrected on this. Probably 90% drop in planes having to divert.
If you book a flight in the winter from a busy airport like LHR then you have to accept you might get delayed if bad weather closes in.
Nigel