When you look at all the evidence from Aliens / Alien 3, there are significant factors against FIORINA 161 being a viable site for mass habitation, besides the weather:
1) There are other candidates.
One of the suits in Aliens refers to there being 'over 300 surveyed worlds' during this period. When you take into account the fact that a full survey is only likely to take place on a world which has the potential to support human life or offer significant dollar return, the number of total planets known and catalogued is probably much greater (gas giants, ice dwarfs etc). Even if only one or two percent of those worlds were ultimately viable, that's still going to multiply the population capacity be several earths (and we can safely assume that Mars, possibly Venus, and several of the larger satellites in our own solar system have already been fully colonised).
2) Distance and sustainability.
Being on the Outer Rim - which Ripley describes as the 'ass-end of space' - and still entirely reliant upon a resupply ship every sixth months is the real killer. The mineral wealth of the planet must have been sufficient to offset the original colonisation / terraforming, but with those resources presumably spent, the cost of maintaining a larger population on a world unable to fulfil some measure of its own consumption would be prohibitive. This is compounded by the presence of indefinitely habitable space-stations like Gateway which, even if they can't provide their own resources, can at least be placed close to planetoids that can supply them.
The real question should be, what does LV-426 offer that makes the 'substantial dollar value' invested in it worthwhile, considering it has similar - though lesser - disadvantages...