Have you considered that there's more to life than just raw pleasure? Engaging with art, learning, experiencing variety, play, etc. Do you think there's nothing that is valuable to do other than experience endorphins? Would lying in a vat and flooding your brain with serotonin for a few decades until it turns to mush really be a desirable life? That's an extreme example, but if you understand why someone wouldn't do that then you understand why someone wouldn't just spend hours of his limited time on earth in jhana every day.
Have you considered that there's more to life than just raw pleasure? Engaging with art, learning, experiencing variety, play, etc. Do you think there's nothing that is valuable to do other than experience endorphins? Would lying in a vat and flooding your brain with serotonin for a few decades until it turns to mush really be a desirable life? That's an extreme example, but if you understand why someone wouldn't do that then you understand why someone wouldn't just spend hours of his limited time on earth in jhana every day.