1. Voyager wasn't as iconic as either TOS or TNG. It's been criticized by people both inside and outside the fandom.
2. It's currently not even aired at all in the United States, and when it last was...it was in the middle of the day on Spike TV so it hardly got any viewers.
3. The aforementioned ratings issue. In first run it got a fraction of TNG's viewers. If a fraction of those fan bought the set, it might not be enough to cover the costs, especially when you consider the added CGI expenses. .
4. By the time they would get around to this (10 years), it will have been about 20 years since it's finale.
5. Chances are by that time, DVDs will be an outmoded form of media, with most paid entertainment being streamed...therefore the "Voyager fans are the type to buy DVDs" would be moot.