Bit of a guess but eg a family of 4 with a fixed 1 week break from work/school.....they have to calculate what they can potentially lose if they must isolate Vs cost of an early Easyjet flight home.I am at a loss to understand how holiday makers have rushed home when para cyclists have an event beginning in Portugal tomorrow for five days.How does that work.
The cyclists, on the other hand, may calculate what they stand to gain if they stay Vs self isolation.
Like you I tried to work out "WHY".