Why don't politician's like cannabis?

I'm firmly in the don't ask don't tell camp when it comes to politicians minor indiscretions in their past (excluding blatant hypocrisy). After all we have all done things in our youth that we are ashamed of (my first ever vote was for the Greens after all).

So what interested me about today's revelations is not that five (or more) Cabinet ministers have smoked dope but the fact that they all appear to have only done it once or twice and not liked it. Is there something in the political genes that makes them immune to the pleasures of THC? And given the legislative hyperactivity that has been the cause of so much problems at the Home Office down the last 10-15 years or so maybe we shouldn't be complaining that Home Office ministers have got stoned in the past but encouraging them to skin up more in the future.