This change in behavior is a signal that the reservoir in question is being utilized very differently, and presumably more efficiently, than before unitization. The answer is, apparently, transactions costs. Resource owners must agree to a split of the profits, a difficult task. Indeed, the task is so difficult that a surprising number of fields are not unitized, even with laws permitting unitization. The following table, extracted from Libecap and Wiggins, shows that while unitization has increased, it is far from widespread.
Transactions costs are, apparently, a major obstacle to unitization, the efficient solution.
Wiggins argue that small leaseholders are particularly likely to hold out, given that they can get a relatively generous amount by extracting, even if their share is of a reduced pie. These same small leaseholders are also political opponents of strong laws forcing unitization. The mystery here is why the efficient solution does not emerge, either as a result of private contracting or as a result of lobbying. In addition, the rule that these covenants run with the land means that a after a resale of the land, a later owner can demand enforcement of the original convenant. Had the same restrictions been negotiated with the original developer as a contract, the restrictions would apply only to the original parties.