In the UK, the rules of sitcom are very different. The BBC commissions a large proportion of sitcoms, so the standard length is a full 30 minutes. Our series (seasons) are typically just six episodes long, and few programmes are commissioned for more than three series.
As a result, huge committees of writers are unnecessary, and most programmes are written by just two people with help from a handful of editors and consultants. Scripts can reflect the idiosyncratic voice of the writers, rather than having to conform to an industrial process where writing can be delegated within a team. Characters and plots don't have to reset to zero by the end of an episode, because there is no expectation that a successful series will run indefinitely.
An obvious comparison would be the British and American versions of The Office. The British version finished after just 12 episodes (plus two Christmas specials), following a clear dramatic arc; The American version ran to 201 episodes. The British version was written wholly by Gervais and Merchant, while the American version had over 40 credited writers. One is a work of art, the other is an industrial product.
The medium is the message.