In a subscription business, you don't want the user to use as few resources as possible. It's the wrong optimization to make.

You want users to keep coming back as often as possible (at the lowest cost-per-run possible though). If they are not coming back they are not renewing.

So, yes, it makes sense to make answers shorter to cut on compute cost (which these SMS-length replies could accomplish) but the main point of making the AI flirtatious or "concerned" is possibly the addictive factor of having a shoulder to cry on 24/7, one that does not call you on your BS and is always supportive... for just $20 a month

The "one-shot correct response" to "I failed my exams" might be "Tough luck, try better next time" but if you do that, you will indeed use very little compute because people will cancel the subscription and never come back.