Chipotle has become an institution for eaters on the go who want a healthy meal. Their restaurants are typically packed with hungry customers, especially during lunch rush hour. Those customers will inevitably appreciate Chipotle's new delivery service because they can avoid traffic and have more down time to enjoy their lunch breaks. Similarly, others at home who do not wish to cook or go out will be pleased to have Chipotle as an alternative to the usual Chinese and pizza choices.
There is a lack of healthy, affordable food delivery services available. Most people are limited to the narrow options of pizza or Chinese food for food delivery. Many people would love to have something different to choose from. The fact that Chipotle has a reputation for fresher, healthier food makes it a natural fit, a missing component of this marketplace.
There isn't much better for semi fast food than what chipotle. With that being said, going to chipotle can be a massive pain in the behind especially during lunch or dinner as the line seems to take forever. If you could call in and get a burrito ordered and delvired in a reasonable amount of time that could be huge for them.
People need convenience and people, in general, are lazy. This will keep many different delivery services in business for a very long time, not just Chipotle. Add to that, there aren't many delivery services for Mexican food. Add to that, the number of Mexicans in the United States seems to exponentially grow daily thus expanding Chipotle's customer base.