So the new workshop/building system seems to be the biggest new gameplay feature..... my questions are:

1. What is the point of building and maintaining settlements, other than for its own sake/because it looks cool/because it's something to do, ala Minecraft? In sanctuary you already have every kind of crafting station available right there in the town. What are the material benefits to constructing anything past what's already there?

2. If you do build a settlement, how does defending it work? Is the placement of your defenses super important, or can you kind of just drop them wherever? Are the traps re-usable or just go off once and then need to be rebuilt? How frequent are raider attacks, and how much/what kind of damage can you expect to take if you do not defend effectively against them?

3. Will settlements be attacked even while you are not in that cell of the map, or will raids only spawn when you travel there personally?

You can use the facilities and resources for yourself. Like the water to heal, you can harvest the food nodes for more materials/ingredients. You can set up trader stores and eventually caravans.

I haven't gone far enough into the game to comment on defences yet but I know that Minuteman dude does patrols around Sanctuary.

From what I've seen you'll get a message telling you that a settlement is under attack and you can fast travel back to help out.