It takes so long because going through a divorce is a process. You have to morn the death of your marriage...yes you do morn it. Then you are able to start healing and putting your life back together as a single person.
i would imagine partly because it takes so long to get over being used, abused and having your heart stepped on by a sociopathic, core-less, selfish trollop.
It took 18 years to start your life, it probably takes a while to do it again... I sure hope it takes a lot less time