The challenge of regression testing faces all development teams. Whenever a team develops or changes some functionality, it has to test it AND make sure that no old functionality has been broken. Teams that rely solely on manual testing often need periods of code freeze and extensive regression testing. It’s not unheard of that this can take weeks or even months for really large, mission-critical legacy systems.
Agile teams that want to deliver at a certain cadence without compromising quality and degrading over time (any team can do one sprint), need to resort to automated checking and a growing suite of tests written by developers to prevent regressions. As time goes by and new features are being added, there’s simply no way perform adequate regression testing without neglecting the quality or postponing the delivery.