From day one, you can do a lot on Stack Exchange without any prior experience at all. Yet if users understand that Stack Exchange users gain certain abilities with reputation, starting with zero (0) suggests they have no reputation/abilities at all.

Everyone starts with one (1) reputation. It's mostly perception and first impression, but saying you have reputation is better than saying you have none at all.

From day one, you can do a lot on Stack Exchange without any prior experience/reputation at all. Yet if new users see that they can gain additional abilities by increasing their "reputation", starting with zero (0) would seem to suggest they are starting out with no reputation/abilities at all.

Everyone starts with one (1) reputation. It's mostly perception and first impression, but saying you have reputation is better than saying you have none at all.