> I can speak to this in some degree

As you suggest at the end, this is very much your personal view.

My wife and I have been together for almost 20 years, but we've only been married for 2. Our commitment didn't change due to marriage. The only thing that changed was that things got easier from a legal perspective. We no longer need to worry about wills in the case that one of us dies, and we can make medical decisions on behalf of each other if necessary.

I suspect that for many people who don't have a religious desire to marry, marriage won't affect their level of commitment. I think this is supported by how often people get divorced.