The problem with lobbying in general is that it's a one-sided information stream: politicians are generally uninformed about a topic and only get the information from the wealthy side (ie. the one able to pay a lobbyist). No need to bribe in general, just overwhelm the poor politicians with "facts" and they have no choice but to walk in line.
To play the devil's advocate: without lobbying, politicians instead get that information from whoever happens to have the resources control the narrative through astroturfing and media manipulation.
Lobbying is at least transparent in its intentions.
