What’s the most underrated SaaS feature that actually drives retention?

We often talk about big features like AI, automation, or integrations, but sometimes it’s the small, overlooked ones that keep users loyal. For example, in my experience, a simple “smart reminder system” has done wonders for engagement.

I’m curious — what’s that one underrated feature you’ve seen (or built) in a SaaS product that makes a real difference in customer stickiness?