俱舍論記 14.160

14.160

「又欲邪行至離非梵行」者，釋頌易離。邪行易離，故佛遮防。離非梵行難故，在家不制。

Regarding "Furthermore, sexual misconduct [...] abstaining from unchaste conduct": Explaining the verse's "easy to avoid." Sexual misconduct is easy to avoid, so the Buddha prohibited it. Because abstaining from unchaste conduct is difficult, it is not forbidden to householders.