The Next Generation Blu-rays didn’t sell well enough to justify another investment of time and money on other Star Trek series, especially considering that The Next Generation was far more popular than either Voyager or Deep Space Nine.
The Star Trek team successfully rebuilt Star Trek: The Next Generation with a process that took several years and many millions of dollars.
The result was a gorgeous remastering of The Next Generation… but the Blu-ray wasn’t released until streaming services became the most convenient way for consumers to watch old episodes of TV.
That said, there is a way to restore content that was originally released on videotape, as long as the original negative is still available.