All games come down to a simple equation when game designers are trying to get players to do something:
Rewards Drive Activity.
In more words, if a game designer wants a player to engage in a particular activity they have to offer sufficient rewards to make the player want to do the activity. The main job of a game designers is primarily one of balancing rewards to encourage the desired activity.
The challenge comes from the fact that rewards can be divided into two very different classes: tangible and intangible. Tangible are very easy to understand and measure; they are explicit rewards given to players as part and parcel of the activity. In EVE, examples would be ISK bounties, Loyalty Points (LPs), standings increases, items... anything that can be objectively compared to other rewards regardless of the player receiving them. For example, if I do Activity A and get 300 LPs and another player gets 400 LPs, I can objectively say she was rewarded more than I was.
Intangible rewards, however, are more complicated and are almost always subjective. Doing an activity like mining that Player Charles enjoys because he likes the zen-like nature of being in space alone with the rocks could be considered very rewarding by him, while I find it mind-numbingly boring and thus the reward being far below the threshold that would make me consider doing it.
Enjoyment of an activity is only one example of an intangible reward. Others include prestige in being known for an activity, power over other people, the joy of trolling or griefing or helping other players, etc. The intangibles are as diverse as the playerbase and thus very hard to plan for.
Ok, so what's my point?
POS moon mining had a very tangible reward (moon goo) and an intangible reward that it required very little overall player participation over time to operate and generate income. Refinery moon mining has the same (or similar) tangible reward of moon goo but a very different intangible reward that it requires a team effort working together to generate the income.
This will appeal to different players as some like the solo POS Silo tending whereas others will enjoy organizing and participating in the group effort to mine the moon debris field. CCP weighed the intangibles and decided that making more players be involved and feel their reward was more important than the fewer players that currently are involved and feel their reward. And that's OK as long as CCP has planned for all of that, which I think they have.
The real question is if the latter approach is rewarding enough to drive enough players to that activity to maintain the current prices of Tech 2 modules and ships.