One of the biggest differences between Taco Bell and Chipotle is that Taco Bell is more reliant on budget shoppers. Meanwhile, Chipotle can charge more for more premium products.
However, when customers aren't willing to pay, Chipotle needs to make changes.
The chain boosted traffic with several give-away deals in 2016, as a somewhat desperate attempt to bring customers back to the chain. The promotions didn't result in the long-term growth that Chipotle was looking for.
However, Taco Bell has found success in building out its $1 menu. The items aren't part of a promotion, and don't cost the fast-food chain much, but are able to bring in customers who don't want to spend much money. With Chipotle's push for new menu items, it's likely some less expensive options get added to the menu to appeal to budget-conscious customers.