I like watching civil war reenactments. Hobbyists  recreate certain battles
I have never seen one in person, but it always seemed odd to me, what is the reason?
Civil war veterans recreated battles as a way to remember their fallen comrades and teach what the war was about
That makes sense I suppose, I would rather just forget about the wars is all, but I do play war games all the time so i guess that is irrelevant
They do it all over, not just here. Canada, Italy, Sweden, Germany and other countries
Do they all have their own civil wars or do they reenact other ones?
They all do their own wars. Time magazine estimates there are 50,000 reenactors in the U.S.
That is a lot, but maybe not that many in the grand scheme of things, maybe they are not as popular anymore
. Civil War veterans recreated battles as a way to remember their fallen comrades and to teach others what the war was all about. The Great Reunion of 1913, celebrating the 50th anniversary of the Battle of Gettysburg, was attended by more than 50,000 Union and Confederate veterans, and included reenactments of elements of the battle, including Pickett's Charge. 
Modern reenacting is thought to have begun during the 1961–1965 Civil War Centennial commemorations. Reenacting grew in popularity during the 1980s and 1990s, due in large part to the success of
Cheltenham Winter Gardens.
Veterans of the American Civil War recreated battles as a way to remember their fallen comrades and to teach others what the war was all about. The Great Reunion of 1913, celebrating the 50th anniversary of the Battle of Gettysburg, was attended by more than 50,000 Union and Confederate veterans, and included reenactments of elements of the battle, including Pickett's Charge.
During the early twentieth century, historical reenactment became very popular in Russia with reenactments of the Siege of Sevastopol (1854–1855) (1906)