What version of Zen Cart are you using?
A bandage was added in 1.3.8 to auto-generate the customers_info record when people did incorrect imports of data.

It would be best to generate the customers_info record while building customer data. The system does expect it to be intact.

In terms of your comment about "marginally useful", you're marginally correct. Without that record, you'll probably get errors during login, or at least the login stats for your customer will be lost.

The upcoming v1.4 version of Zen Cart expects the customers_info data to be intact during the upgrade while it merges the 2 tables into one, essentially minimizing the problem you're complaining about.