When I first started dancing, I used the Yellow Pages to find studios. At least of third of the listings were for studios that either no longer existed or had relocated.
You use the phrase "kept updated with current information" as though doing so is a simple matter. Even moderately sized corporations require staffs of professionals to keep complex websites current.
Also, maintaining their listings in such a directory would put a real burden on the (usually small) staffs of most dance studios who are already busy with their own sites.
Web searches are certainly not "one of the worst ways to find a dance studio."
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