Yet it is neither rare nor without theoretical interest.

These compounds are not common but are of theoretical interest.

These cases are not only common, though hardly ever in the much over-simplified form we have considered, but also of some theoretical interest.

Does it have practical implications or is this just of theoretical interest?

But this is essentially of theoretical interest only, and there are far more practical examples.

This anion has been of great theoretical interest to the chemistry community.

Thus the general case where is of the theoretical and practical interest.

The analysis by Professor Arrow was long thought to be of only theoretical interest.

Although not a practical programming language, Unlambda is of some theoretical interest.

But at the moment, the question is of more than theoretical interest, isn't it?