If ever there was a strong argument for why the system of selection ought to change toward a route where people have to compete in wider elections in order to stand for election it has to be the following observation by Sir Humphrey Appleby.
"The argument that we must do everything a Minister demands because he has been 'democratically chosen' does not stand up to close inspection. MPs are not chosen by 'the people' - they are chosen by their local constituency parties: thirty-five men in grubby raincoats or thirty-five women in silly hats. The further 'selection' process is equally a nonsense: there are only 630 MPs and a party with just over 300 MPs forms a government and of these 300, 100 are too old and too silly to be ministers and 100 too young and too callow. Therefore there are about 100 MPs to fill 100 government posts. Effectively no choice at all."As with pretty much anything in politics, the opposition to open primaries is all about power.
Local associations or CLPs hate the thought of letting the ordinaries be involved. They'll happily take your vote on polling day, but woe betide anyone that thinks they might have the judgement to pick the right person to stand in the first place.
The most amusing thing for me is that those who argue about the importance of a local Tory association in candidate selection rarely seem to comment upon how open to abuse the status quo actually is.