Perhaps there should be a sticky on this topic. An official post as to why they chose the subscription model, why it's the correct decision, and how a player could potentially play the game entirely for free.
I know NQ has made official statements over and over, but perhaps a sticky that transcends all boards would be beneficial. What I mean by this, is I know that other forums I have visited have the ability to make a "global" sticky, where it shows up in every section of the forums.
Although it's annoying to have to answer the same gripes over and over, there is no need to belittle them. Best to just let someone else with more patience answer the question.
As an aside, if you haven't figured it out yet... as Tumeden put it keeps the servers running. Now, depending on how many lifetime subs they sell... they may lose a large margin of that dedicated cash flow which is disappointing. Furthermore, having a subscription model helps with keeping the integrity of the game as well. If we were to delve into a b2p with micro transactions, it would most likely negatively impact the integrity of the game. This could happen through multiple avenues, depending on which microtransaction pathway was taken. If it were purely cosmetics, then people could potentially be flying around as unicorns. On the same line, if they added pets there would be unnecessary clutter. (Now, you're probably thinking they already added pets... however, this was in a limited fashion and it looks like they won't be selling pets later). On a different pathway, if they followed a system similar to Star Citizen and sold blueprints... obviously the game would be completely different. It is no doubt that Star Citizen would be a completely different game if they didn't sell ships, and that is disregarding the hit in funding they would take if they didn't. Granted, the argument there is SC is "supposed" to be 90% NPCs. But does that really matter? I'm not saying CIG has done anything wrong, just that it would be a different game with a different atmosphere otherwise.
tldr; the atmosphere of the game could take negative hits depending on the funding model. One of the major reasons I backed DU is because it has subscription models.
*sorry for any typos or grammatical errors, typed this up in a jiffy.