A full programming language gives too much flexibility. In particular, this includes the flexibility allowing to shoot oneself in the foot.

A person who constantly works with computers is painfully aware of the people's ability to screw things up by an honest mistake when programming them. The more complex the thing, the easier it is to make a mistake, because human attention is finite.

Whenever you can limit the language to the task at hand, and build in guard rails that would prevent you from doing things you should not be doing, it's usually a productivity win, even if it precludes implementation of 3% of some most advanced and complex solutions. Reliability and simplicity go hand in hand, and reliability is often the thing devops people value very highly.