Some feedback.
Well, if its very rare and much sought after, a probable justification would be that non-fringe systems are much more explored, prospected and..mined (out). It just makes sense man.
There is really no reason for humanity NOT to build the Hutton Orbital research station.
1. It is the first system that really got explored I think (and the closest star system to earth). Hutton Orbital is a research station (also one of the first built/maintained), and you put these out where there is actually something to research. Not where it is convenient for trade or colonization.
2. With the advancement of the FSD (lore-wise), getting to the station takes mere hours. Before it, it would take months. If humanity put a research station there (as per FE2/FFE lore) and then kept resupplying it with multi-month duration missions, would they even blink if the traveling time went down to hours?
Thus, I think you are equating your gameplay time with what would seem probable, plausible or appropriate in the game world lore.
Don't get me wrong, I would love to see in the future micro jumps between the stars of a multiple star system (FDEV have hinted on that). But that does not make HO improbable from a universe/lore point of view imo. Far from it.