A year or so ago I did some research into this and discovered that, if I remember the number correctly, at least three different fire authorities had recorded incidents of fatalities resulting from wooden tea-light holders without inflammable barriers, becoming so charred and dry through frequent use that they eventually combusted. However, most trading standards offices require there to be a non-inflamable interface, which is currently provided by the aluminium pot that the tea light is sold in. Clearly, the aluminium pot is not up to the job of acting as an interface in a wooden tea-light holder, but where there are relevant trading standards, they appear to meet these standards.
All we can do is educate and keep plugging away!
Les