The UK government has committed to paying out GBP 6 billion a month to pay peoples wages/salaries. The 14 day quarantine should have been implemented back in March if it had anything to do with keeping infection rates down in the same way as many other countries were doing, including Cyprus.
The reason it’s now being implemented in the UK at the end of this month is because many other European airports will be starting to open up in June.
What the UK government definitely does not want is to see it’s citizens leaving the country and spending all of that money that’s been given to them abroad.
No one wants to enter the UK with such a high infection rate, so the quarantine won’t be effecting potential incoming tourists, it will only affect those who want to leave the UK who will not bother with the impending quarantine on return.
The UK government is in effect trapping it’s own people in the country so they have to spend their money there and nowhere else.