Personally I think driving around alien world's and shooting rocks to gather exotic and rare materials such as iron is an excellent mechanic.
Imagine if you could just buy it, for money. It would be terrible.
Thank you for bringing up my pet immersion breaker. It's the first of many examples I used to give FD as constructive feedback. Followed closely by instantaneous data transmission across the galaxy (multicrew telepresense).
Two points...
It's not just the absurdity of these (and many other) immersion breakers. One could almost (barely) accept instantaneous data tranmission at unlimited distance
if such technology was used elsewhere in the galaxy, but it isn't. The inconsistency is just as much an immersion breaker. You can buy gold, but you can't buy iron. And why? Because iron is used by Engineers. What??
Secondly, I am at a loss as to David Braben's input. Here's a man who prides himself on creating an excellect PG galaxy simulation, passionately describing the accuracy with which the various system bodies are created, and yet he lets the gameplay be designed with such verisimilitude failures. Weird.
I see so many people saying it's just a game, and... "gameplay". Yup, true. But the two bad game design examples given above could easily have been designed without the current absurdities, as dozens of old threads have shown. FD, please put as much love into gameplay development as you have with the PG galaxy.