What good might it be good or helpful for someone to know someone else's path to faith?
Here're three reasons:
Makes it personal
Conversations with folks about coming to Jesus can be incredibly abstract, confusing and esoteric. Christianity isn't another philosophy (although it sounds that way from time to time) and coming to faith in Christ is a very different experience from coming to believe an abstract idea.
I still remember when Mr. Morin joyfully explained to us that, if we applied differentials properly, we could calculate acceleration if we knew velocity. I remember sitting in Mr. Cano's physics class and testing out Mr. Morin's claim and finding that it worked. It really worked! But that's not the same experience I had when I came to know Christ.
A testimony matters because coming to Christ is personal, not abstract. We come to a person, engage with a person, ultimately, not an idea or a principle or a theorem. Telling my story of how I came to connect with that person can guide people away from the abstract and toward the relational.
Some people wonder if God can really rescue them. We hear a lot of that this time of year. People have just slogged through rush and some have done some things they regretted. Does God want me? Can God reach me?
Knowing someone else's path to faith can be marvelously faith-inducing. Again, it has to do with making the experience a little more concrete. "This is how I connected with Jesus" can spark in people an echo, a "Maybe I can connect with Jesus that way as well."
Building for the long-term
Lastly, we're building for the long-term. Telling someone an honest account of your conversion experience can give them a heads-up for what they're getting themselves into.
I think, and I don't have any hard evidence to back this up, that one of the main reasons we see so many people grow up in Christian homes and then go off to college and not follow Jesus has something to do with no one building for the long-term. We build temporary housing for the spiritually homeless, wanting to get them connected and committed.
So we petition and persuade. We manipulate and cajole. We cover over the rough spots so that this whole thing looks more attractive. And that's wrong. When we do that, we set people up to wander away. If I get started on this Jesus-thing and, all of the sudden, am facing all kinds of opposition and conflict and turmoil in my family/friend-group/community, how would it feel to know that this happened to you and you gave me no warning?
If we build for the long-term, we let people know what they're getting themselves into, at least in part. And we do that by telling them our story. Not just the story of the Pollyanna, I'm-in-love days, but also the story of the struggles and dark nights. We don't want to scare people away, but we also don't want to bait and switch.
Remember, we're called to be "fishers of men."