Why do many British people get into the habit of carrying umbrellas when they go out for many years?

In Britain, the weather there is always changeable, and sometimes it suddenly rains heavily in clear skies in Wan Li. If the weather forecast is correct, people there will also be affected by bad weather and get soaked. People often complain about the meteorological station, because no one can predict what the weather will be like the next day, so everyone has developed the habit of taking an umbrella when going out, and because the weather is like this all year round, they have developed the habit of taking an umbrella when going out for many years.