What would happen if everyone became a monk or nun?

Theravada Buddhism holds that achieving nirvana is impossible for a lay person, hence my question. > "When this was said, the wanderer Vacchagotta asked the Blessed One: “Master Gotama, is there any householder who, without abandoning the fetter of householdership, on the dissolution of the body has made an end of suffering?” > > “Vaccha, there is no householder who, without abandoning the fetter of householdership, on the dissolution of the body has made an end of suffering". > > - MN 71 (Tevijjavaccha-suttaṃ)