Dunno why you're being down voted, it's a legitimate question. Our electoral system is the reason. Only the highest vote percentage gets into government. So third party candidates can only be spoilers in most elections. To prevent that, the two major parties scoop up any serious third party candidates, or do their best to discredit them.
There is a recent change in a few states to ranked choice voting, that aside from selecting more centrist candidates, also gives legitimate third party candidates a place. Still not enough really get them off the ground, but very much a way to make voices heard without sacrificing a seat in government.