2. You think you will make friends. There's something about the total immersion effect that makes friendships. I still workshop with three others from my course ten years down the line, and am in touch with many more.
3. You think you will learn about writing. Not so much the craft, as that doesn't seem to be taught except by the osmosis method, but the intensive workshop process that is at the heart of most MAs is the fastest way to learn to critique others, and by critiquing others, to learn to self-edit.
4. You think it will help towards publication. A tricky one this. I'm undoubted published because I went on the MA, but I don't think the course directly got me published. Certainly there were fewer agents and publishers buzzing around than one hopes before starting the course and in hindsight the advice about the real world was risible. But learning to workshop, discovering writing friends, and immersion in writing were all crucial in becoming published.
Overall I loved my course, but maybe I'm biased because I've been lucky enough to make my living from writing ever since. I know a lot of people who feel they wasted their time and money.