Hmmm... The general rule I see in play here is "Overindulgence leads to pain
While it is true that overindulgence does generally provide pain, I would see that as an uncontroversial point and therefore unlikely to be the reason for its inclusion , and especially for its inclusion in the manner it is written.
This exchange may seem pedantic but I think there is a lot more going on here than just the two of us talking shop so I think it's very useful!
My motivations are directed at what I perceived is a problem that I link to Martha Nussbaum's "Therapy of Desire." I think it helps to consider whether Epicurus was primarily a clinician or a revolutionary philosopher. In the end he is both, but the modern worlds excess emphasis on the clinical aspect has in my view led to under-appreciation of the revolutionary implications of the philosophy.
"Everyone" accepts that overindulgence leads to pain, but "pleasure is the highest good" and "even the pleasures that some deplore are acceptable if they bring happiness to the person we think deplorqble" are words that wars get fought over.