I think the main reason, nowadays, why food and drink is provided 'in house' for MPs is security. Unfortunately, we live in a time when some people think they have a right to take action against others for a whole variety of reasons. MPs need to know they can enjoy a lunch break without being set upon. They often need to be close to the action if the division bell goes, they have a meeting with a constituent or they are meeting business people in the context of their work. In the H of C they can leave their meal, vote and return. I think it is easy to go into punitive measures as a member of the 'enraged' public when the drinking culture is exposed in newspapers as it has been recently. Most of us do not experience harassment when we go out to eat. The drinking culture is another issue which could be tackled with restrictive hours. MPs have a right to be able to discuss the matters of the political day in a private setting rather than the local pub where journalists, and the public, can overhear them.