The world of Alien is odd.

The Nostromo has this great big refinery on the back for processing mineral ores which it has extracted a great distance away from Earth.

This suggests that it's financially worth Weylan Yutani's while, so either it forbidden by extreme regulation to mine more locally or our native system (and any colonies we have beyond the Solar system) are so depleted that we have to cast a wider net.

Which doesn't make sense in the time frame we now have thanks to Prometheus.

So if these Mega Corps are highly regulated to the extent that they have to pick up ores from other star systems, who is regulating these companies?

Strong national governments goes against the evil corporation model the series is pushing.

It's debatable if Tyrell is forced to allow human Deckard investigate his company or if he sets replicant Deckard up with false memories to investigate other missing replicants for the sake of Tyrell's safety.

If that concession to the law is a political illusion maybe these 'limitations' to local ore mining are to prevent corporate wars or something.

If Tyrell can implant the memories of others into replicant brains what's stopping Weyland from having a mind scan and just duplicating himself at the point of near death for all eternity?