Although no couple is required to do NFP, they can certainly can be providential if they want, for those that want NFP there are plenty of classes and resources.
That may be your impression, but I strongly disagree with your affirmation. There is no plenty of class and resources available for everyone.
Our diocese requires NFP classes during premarital preparation.
A paradox. Why force NFP classes if NFP is not requires in marital life. And why force couple who know in advance they are not fertile?
Why to force a couple if taking a class is unpractical for them, for eg because of distance or because they are unavailable?
Finally, the NFP class take longer time
What percentage of people possiblity renouced of getting married because of that?