This looks like the only reason to, all the other responses seemed to be something like: because it costs nothing to train it at the same time than combat.When new monsters come out that drop new items that are worth ALOT the first lil while they are out usualy come from monsters that take slayer to kill them, my brother has made alot of money from this lol
You can earn a shat load of money from it and it's useful for new realeases and mini-games(sw)
If you want shit loads of money with combat, you can do frost dragons or green dragons or anything that will yield more money than slayer in the same alloted time. If you want a shitload of charms you can go to waterfiends or whatever and you'll get a lot more charms. The only point that slayer gets is the new releases thingy.

