The U.S. Army hoped to save a lot of money, and improve morale, by allowing all troops in South Korea to bring their families. But problems have cropped up. The obvious one is housing. There's little on-base housing, which is the most attractive for military families. Another problem is isolation. Although there's a consolidation underway, there are still many small bases, scattered all over Seoul and along the western portion of the DMZ. Then there's the traffic, especially around Seoul, which is jammed up like Atlanta or Los Angeles. You waste a lot of time trying to get to a shopping or medical facility your own little base doesn't have. Worst of all, there are few jobs for spouses, even when there isn't a recession going on. Given all that, many married troops are inclined to take the shorter unaccompanied tour, at least until everything becomes more family friendly.
Currently, there are 2,800 command sponsored (the military pays transportation) families in South Korea, with another 1,500 due in the next year. In addition, there are 1,700 families that paid their own way over. Thus by next year, there will be 6,000 families in South Korea, meaning about half the married troops will be "accompanied" (by their families.) There are about 25,000 U.S. troops in South Korea, some 85 percent of them army.
To come over with your family, troops have to agree to a two or three year tour in South Korea. They will also get an additional $300 a month, because some of the U.S. bases are still out in the boondocks, and families will not always be living at the same base as their soldier works. Lots of commuting. There are still a few bases that, for a while yet, will still be only for troops on hardship tours.
For as long as U.S. troops have been there, they served one year tours in South Korea, and could not bring their families with them. Going to South Korea was known as an "unaccompanied" (by family) tour. More colloquially, it was called a "hardship tour," but it was only rough on the married troops. The single guys, and many of the married ones, took advantage of the cheap booze and inexpensive prostitutes to take the edge off the "hardship." But in the last three decades, South Korea has turned into a first world economy, with all the amenities that Americans take for granted. The hookers are not only more expensive, but increasingly illegal. South Korea is now more like Japan and Germany, which have been off the "hardship tour" list since the 1960s.
At the same time, the U.S. forces in South Korea have shrunk from over 100,000 troops in the early 50s (after the war ended), to 25,000. These days, the well equipped South Korea forces are believed capable of handling any invasion from the north. At the same time, communist North Korea has suffered famine and economic collapse since the end of the Cold War in 1991, and the end of Russian and Chinese subsidies that propped up the mismanaged economy. The North Korean military has, especially in the last decade, declined because of fuel shortages, which limited training. There hasn't been much money for new equipment, either, and the current stuff is falling apart. The North Koreans are still a threat, but South Korea is more worried about the human and fiscal fallout from a collapse of the North Korean government, than a reunification of Korea. That chaos will be paid for by the newly affluent taxpayers of South Korea, and the policed initially by South Korean troops. The small American force will, as always, be there mainly to guarantee U.S. reinforcements if the Chinese march into South Korea via North Korea, or the North Korea come across the border and get lucky.