The problem with that thought is, when they become contagious (symptomatic) then they'll need treatment. The thing is, unless you decide to just not treat them (mortality rate goes up) then the same people are at risk even with a quarantine in place. The fact that, even without mandatory asymptomatic quarantines, the only people who've gotten infected in the U.S. are two nurses that treated a symptomatic ebola patient. Quarantines are not necessary.
Quarantining people to ease public perception are a completely different thing, however. The public is a twitchy, panicky beast and we all know it. If pointless quarantines are what it takes to calm the beast down, so be it.