As they learn more about the local natural resources, they’ve become less reliant on that, but they’re still not 100% independent. Sometimes it’s a matter of a specific skill that’s missing, e.g. if they don’t have anyone who knows how to make X, then they have to either import X or find an alternative that they can produce locally.
They don’t have the means to produce all of the materials needed to build a house like this in this settlement. So some of the materials have to be brought in, one way or another — preferably by teleporting.