I've met many 26 year olds who couldn't even name Galloway, and yet I've met some 16 year olds who have active interests in politics at local and national level. I don't think it's an age problem, it's a social one.
The turnout at the last General Election was below 70%, which means over 30% of those over 18 and eligible to vote either took no interest or deliberately avoided voting. Some 16-17 year olds will vote if given the opportunity (I certainly would have done at that age) and some wont. Just because not all of them would is no argument from preventing those who want to vote having the right to do so.
Former Tory leader and current Foreign Secretary William Hague made quite a name for himself at 16 (though I'm not sure if that's an argument in favour or against the idea of votes at 16, tbh )