Because the people calling the shots don't understand the "market". They've been coasting on their (predecessors') early success for years. Their numbers with respect to audience size is dependent on the same factors that OpenOffice depends on: people with a faint awareness of what the project is / once was but no real exposure to the ins and outs of what has changed about the projects in the last several years.

Short answer is that the amount of time and energy to create and maintain it wouldn't be justified by the expected gain.

I'm not even sure what moz would gain here.