Invest in tether is not a good way for profit and you can not trade tether with real dollars. Anyway, if it is tradable, the trading fee will kill traders who want to trade tether with dollars.
The value of tether remain stable with the value of dollar that is why it is not profitable to do trade in tether but people often keep their money in tether if they feel all the coins are dropping but now as Bittrex has added US dollar to the bitcoin trade so people can shift their money to there but I also not suggest that as the market after drop suddenly start to recover and we know after the price rise and at that time if we will buy then we will lose some value in bitcoin.