Lobbying informs decision makers, in a non-neutral manner, about what they regulate from the perspective of people actually subject to the regulation produced. That is a very valuable thing if you compare it to the alternative. In societies where this is absent it leads to incredible inefficiency (just ask an old Dubai taxi driver about why a building was built, for instance. Prepare to be amazed).

Lobbying provides a form of feedback that would be very hard to acquire otherwise. Neither policymakers, nor the democratic public can realistically study the entire economy in sufficient detail to regulate it. But by definition, there are people who have made it their living to study, work and use parts of the economy, and they should be given access to policymakers before they get regulated.

And that's of course where it should stop. Oh well.