Although they are recorded - it may be difficult locating the true owner. Many date back multiple generations with multiple heirs who might not even realize that they own it or just don't care. In some cases, these folks (or corporate successors) might be located via companies interested in mining/drilling the property (and only if they decide the rights are worth something). However - in the large majority of cases - the rights sit with little prospect they will ever be used and without clear ownership. As an earlier poster said - it would make sense if there was some scheme to revert the rights back to the surface owners after a fixed period of time - whether it be through property taxes or some other legal mechanism (such as declaring abandonment).
In any case - my two cents.
Joe