The man who lives with a wife has a great responsibility in maintaining the members of the other social orders — the brahmacaris, vanaprasthas and sannyasis. Except for the grhasthas, or the householders, everyone is supposed to engage in the spiritual advancement of life, and therefore the brahmacari, the vanaprastha and the sannyasi have very little time to earn a livelihood.
Srila Prabhupada, SB 3.14.18, ppt.