With the approach of the more Agile concepts like Extreme Programming (XP), Paired Programming and Test-Driven Development (TDD), we discovered techniques to build software reliable, durable and affordable.
All these methodologies have a single goal to speed up development, to discover major bugs earlier, and build a lot more product and faster than is possible with other methodologies.
You need a level of testing to make a product release-ready. By their nature of focusing on the crucial bugs, extreme Agile methodologies can’t give you this assurance.