What I find interesting is the jump to acceptance based on the society they're living in.
The Christian becomes a Christian or just "is" a Christian in a Christian environment participating in a Christian society.
The agnostic looks at the Earth and sees many systems, many histories. This creates an opportunity to explore, perhaps before making a decision. Although for the most part, in my opinion, the journey never really ends.
I believe those two observations may hold the fundamental differences between a need, if you will, for knowledge and an acceptance based on faith.