As good as it is it has just never found an audience.
Indeed. More4 had The Daily Show on for a few years, but dropped it after the audience proved too small. The Colbert Report was also on FX Channel (now FOX) for a couple of years too. However, lack of audience and cost were cited as reasons for dropping it.
The same thing happened on Comedy Central Extra, who had The Daily Show on at 11pm for a couple of years until early this year, but then started messing with it, pushing it back, missing some episodes and then putting them out at 1am or 1.30am before dumping it.
In addition to the niche audience, they also have the issue of finding something to put on on a Monday night (the show airs Mon-Thurs in the US, replayed Tues-Fri in the UK), and also filling the gaps when the show takes a break. Not big issues, but if the audience is small, you can see why the channels just decide not to bother with the hassle at all.
I hope it stays on Comedy Central for a while, especially given the Presidential election next year.