I personally have never heard from a product person „Let’s A/B test whether this is delightful“. And I think that’s because delightfulness or satisfaction is impossible to quantify in A/B tests. You only get to measure things like engagement, signup rates, retention etc. - cold hard taps on the screen, and no more.

And I must say that I‘m glad that, right now, apps can’t just scan my face (or cortisol levels, or pheromones or…) for emotional clues while I read their pesky push notifications that want to coax me back into their daily active user base.