Why is there a revolving door between Congress & lobbyists?

Recent studies have found around 30% of the House and 50% of Senators go into lobbying or a related position after retiring from congress. The revolving door of influence creates an incentive for members of congress to cater to the industries they regulate when their responsibility is to the public. The BLAST Act, introduced by Sen Warren, with significant bipartisan support, aims to get rid of that incentive by banning members of congress from taking high paying jobs as lobbyists for life.