Then there's also the fact that D1 was not readily accepted at the time for being a film to video tape transfer method.
This is a quote from "Video Editing: A Post Production Primer Fourth Edition" by Steven E. Browne published in 2002 (you can check out the quote here: http://www.tlu.ee/~rajaleid/BFF6193_...Primer-4ed.pdf
on page 6 of the PDF --- page 10 of the scanned book)
D1, an expensive, extremely high-end product, was used for effects and graphics. D2, a less-expensive digital medium, made inroads into the higher-budgeted production and postproduction environment and as a film-to-tape mastering format...while D2 was used for some graphic and animation product creation.
So even though D1 may sound like the better format for the editors to use, it has a number of strikes against it, with the biggest one being that for film-to-video mastering, it was not the format that was being used. And the high cost of D1, as someone mentioned in the Season 2 forum, would've been a major detractor to the producers of TNG and DS9.