Every interaction with a customer or even a potential customer can provide you with data that you can then use to gain and keep their attention. It is a key element of personalisation - something that makes interactions with your brand much more memorable and enjoyable, and can drive engagement and conversion as a result.
For example - you wouldn’t (or at least, you shouldn’t) send the same emails to loyal, regular, customers as you would to someone who hasn’t made a purchase or even opened messages for a few months. They’re likely to be in very different stages of their customer journey and, by extension, their relationship with your brand. By tailoring your communications you show you’re paying attention to your audience’s needs, and care about giving them a personalised experience.
The key benefits of email segmentation

Email segmentation leads to higher engagement, which increases the chance of conversions.
Targeted campaigns keep customers loyal, strengthen their relationship with your business, and increase the likeliness of repeat purchases being made.
Email marketing can reduce cart abandonment by sending indecisive customers reminders and personalised incentives to convince them to complete their purchases.