The thing is, a lot of them do. Germany is outside most refugee routes (most of the people in Calais never went through Germany) but they get people from Eastern Europe fleeing westwards. But France has way more refugees per capita than the UK, and way more in absolute numbers. Seriously, have a look here for example, it’s ridiculous: https://en.m.wikipedia.org/wiki/List_of_countries_by_refugee... .

Those who try to cross the Channel planned to come to the UK since the beginning of their journey, mostly for cultural reasons.