I have built several sites now with EE and none of them have had comments until I added it only this week to a site I am building - so not you don’t have to have them!
However in your case I think comments on articles is a great idea as you will have a good long topic to create discussions and you can build on this to create a community around your site - good example of this are the articles on http://www.alistapart.com. Next issue then is when to turn the comments off. With articles I would leave them always open or until a newer article supercedes the first one (and then link them). Blog type diary posts though I would turn off within a short amount of time to keep to activity on the newer posts.
Of course everyone does it differently!