Because it's been a seller's market for the past couple of years, hotels have begun to include attrition clauses in their contracts. Hotels have instituted these policies because they feel powerless to do anything about attrition. They are at the mercy of other people during the housing process, and there's been no other way to directly address the problem other than to hold planners accountable. Dealing with attrition is everyone's problem. Planners don't want to pay the extra cash to hotels, and they also feel powerless because there is no easy way to deal with it.
Meeting planners do have convention history reports, but no tools for trend analysis.
For several years now, the industry has supported the idea of collecting deposits as a way to fight attrition. But some people circumvent the process. Let's say an exhibitor goes to 6 or 8 conventions a year. They'll reserve 6-8 rooms thinking they might need them, knowing that after cutoff they can cancel without penalty as the hotel doesn't know who they are and can't hold them accountable or the exhibitor can dispute the charges and credit card companies will refund their money. So they really have been able to abuse the system, creating problems for the meeting planners, the associations, and the hotels.