Predictability is expensive. For example, a Lexus will cost you more than your average American car, but with a consistently high reliability score that increases with each new version, it makes the higher price justifiable for many consumers (And the Lexus owners who can't remember the name of their mechanic would attest to that!)
Of course, being expensive doesn't always translate into providing more value. But when it comes to providing predictable, stable, results, I'd argue that the benefit is worth the cost. It's expensive to deal with irregular work that breaks as often as it works. If predictability is so valuable however, why don't more Joomla development companies focus on it?