In my tour of Athenian religion, I've noted that many of the leading Greek philosophers were charged with impiety by the Athenians. First, Anaxagoras in the 5th century, then Socrates. Aristotle was charged with sacrificing to his late wife and her father Hermeias, Tyrant of Atarneus (Troas). Socrates chose death, the other two exile. It strikes me that we might place too much emphasis on writers like Plato as sources for Greek religion, since both his teacher (Socrates) and his student (Aristotle) were officially charged by the state and tried for impiety.
My suspicions were aroused when reading that the so-called Orphic gold lamellae from Thurii were produced by a Pythagorean and/or Orphic sect. Orphism now believed to be a largely modern creation, but Pythagoras existed and had well attested successors. But was there are large Pythagorean 'sect' in Southern Italy, whose existence is 'proven' by the discovery of the gold lamellae? I doubt it.
Pythagoras had a definite following in later 5th century BC Crotone, mostly as a result of his work in science: we still use his theorem when calculating the internal angles of triangles. How many followed his lifestyle 'prescriptions' is less clear, and the emphasis we put on his important scientific discoveries has skewed the evidence - just because he was admired as a mathematician does not mean that the people of Crotone adopted his lifestyle wholesale.
In fact we know that the men of Crotone objected to his preaching marital fidelity, which went against the grain for Greeks.
The 5th century BC philosopher Empedocles used the story of the Titans cannibalising Dionysus to justify not eating meat, and advocating Pythagorean practices of vegetarianism. Vegetarianism was equally problematic to the Greeks: it put one outside mainstream society, since it meant one had to refuse to make or eat animal sacrifices made to the gods, and this in turn placed people outside the normal order of state religion. Even today vegetarians can struggle. Pythagoras and a few of his followers took purity to an extreme, and by doing do marginalised themselves to the point of being seen as 'deviant' by other Greeks.
Pythagoreans were told to wear linen rather than wool. An inscription from Delos tells us that the wearing of wool was banned within the sanctuary of the Egyptian gods. Herodotus (2.37.2) notes that the Egyptians wore linen for rituals, and not wool. Since Pythagoras claimed to have studied with the Egyptians - a claim many philosophers made to explain their superior knowledge - his prescription that his followers wear linen rather than wool may have been an affectation based on his 'Egyptian background'. Linen shrouds were found in the Thurii tumuli, but shrouds were often linen. It might not have been as practical as wool in the wold though.
Overall we can conclude that few followed the 'Pythagorean' lifestyle in the Classical period, and that it did not become popular until it was adopted by the late Neoplatonist philosophers. The gold tablets from the are can better be understood in the context of a local cult of Persephone, such as the one known at Locris.