It seems in the ones that I like, that there was a reason for the portal or that there was story that dealt with the portal in a way that it just wasn't the convenient macguffin that allows a passage but other than that has no life ramifications for anybody.

That's a good point. And, in point of fact, one of the handwavium bits from when I was twelve that I've never satisfactorily renovated. (This idea's been with me a long time, and needs a lot of work.)