If that were true, Sentai or ADv would have released another set.
Sentai does not have any obligation to print/re-release another DVD set, just because they have the distribution rights. For all we know, there are variables that prevent them from doing so, e.g. getting permission from the production studio and its parent company, paying royalties to the voice actors (many of whom, retired within the past decade), dealing with other domestic distributors, etc etc.
But if it makes you feel any better, the BD Remasters have been cancelled. Due to "technical issues" and lack of market interest.