I don't have a problem with it in theory.
The problem is that, as all games prove, there are people who simply enjoy making life miserable for others.
In ED those people have, at least, got to spend the time getting themselves into a position where they can act that way.
If you could buy credits/ships/weapons then it'd probably be fine for a lot of people but it would undoubtedly increase the number of griefers to be found.
That being the case, you've got to admire FDev for restraining themselves from indulging in a lucrative opportunity that would damage gameplay.
The way I see it, a tw*t is a tw*t, whether they had to spent time or not before being in a position to demonstrate it is, ultimately, irrelevant. And the amount of time required is frankly pretty small, new get-rich-quick and get-rank-quick schemes are continuously discovered. So if that crowd will get there anyhow, why not cash in on them?
The pitfall I see in non-cosmetic sales is not player related but company related. It's the temptation for the company to start artificially increasing the time-to-reward to make the cash store more and more convenient until it's the only actual option (like all those mobile clicker games for example). This, obviously, negatively impacts everyone.
Still, I'll leave it at that as it's a bit of an off-topic drift (but an interesting one).