Because the day after the stupid Obama-drinks-too-much smear was debunked, UK's Mail, no doubt trolling for RW links, runs with the story:

Headline:

Barack Obama should drink less alcohol and try harder to kick his smoking habit, doctors says

The lede:

Barack Obama should not only try harder to kick his smoking habit, his team of doctors warned, but they also recommended 'moderation of alcohol intake'

And yes, the Mail implies Obama's drinking too much [emphasis added]:

It would seem the pressure of the U.S. presidency - and all those White House receptions - are taking their toll after the 48-year-old's first medical checkup since winning the race to the White House.

The British press printing lies about Democrats? Sadly, it's nothing new.