I realize I’m late to the game here, but…
The idea that Epicurus was an ascetic and ordered an ascetic lifestyle for his students seems to stem from two primary sources: the idea of the “necessary and natural” desires, and the mention of “bread and water” in the Letter to Menoikeus.
As for the latter, I’ve stated in other places (including my translation of the letter), I am convinced that Epicurus was using “maza and water” because that was the everyday meal of the regular ancient Greeks. Epicurus is referencing the meal you have every day and don’t even pay attention to and contrasting that with the extravagant table laden with fish and other delicacies. He’s urging us to pay attention to the meal that’s in front of us. We don’t have to shun luxuries should they come up every once in a while, but we have all we need right here in front of us if we pay attention to it.
The natural and necessary desires are never singled out as the ONLY desires to pursue or fulfill, although he says that’s all we *need* should that befall us. We aren’t commanded to only pursue those… and there is some question in my mind what those “necessary and natural’ ones are since he’s a little circumspect in the letter to Menoikeus 127-128 (see below). Most of these, to me, encourage us to pay attention to our needs and desires; not necessarily what to choose. Everyone has to make those decisions for themselves.
VS63 is a good one to bring up. Bailey’s commentary on that one is LXIII is interesting as showing that Epicurus did not wish to push his idea of the simple life to excess: the ascetic will suffer bodily distress like the glutton and so fail to attain aponia.
Menoikeus 127-128:
Furthermore, on the one hand, there are the natural desires; on the other, the 'empty, fruitless, or vain ones.' And of the natural ones, on the one hand, are the necessary ones; on the other, the ones which are only natural; then, of the necessary ones: on the one hand, those necessary for eudaimonia; then, those necessary for the freedom from disturbance for the body; then those necessary for life itself. [128] The steady contemplation of these things equips one to know how to decide all choice and rejection for the health of the body and for the tranquility of the mind, that is for our physical and our mental existence, since this is the goal of a blessed life.
PD29 Among desires, some are natural and necessary, some are natural and unnecessary, and some are unnatural and unnecessary (arising instead from groundless opinion). (Scholion on PD29: Epicurus regards as natural and necessary desires which bring relief from pain, as e.g. drink when we are thirsty ; while by natural and not necessary he means those which merely diversify the pleasure without removing the pain, as e.g. costly viands ; by the neither natural nor necessary he means desires for crowns and the erection of statues in one's honour.)
Seneca, Letter 9.20 (quoting Epicurus): “Si cui," inquit, "sua non videntur amplissima, licet totius mundi dominus sit, tamen miser est." "He says: "Whoever does not regard what he has as most ample wealth, is unhappy, though he be master of the whole world."
Seneca, Letter 14: Now you are stretching forth your hand for the daily gift. Golden indeed will be the gift with which I shall load you; and, inasmuch as we have mentioned gold, let me tell you how its use and enjoyment may bring you greater pleasure. “He who needs riches least, enjoys riches most.” “Author’s name, please!” you say. Now, to show you how generous I am, it is my intent to praise the dicta of other schools. The phrase belongs to Epicurus, or Metrodorus, or some one of that particular thinking-shop.