31P and 19F, or have very high natural abundance, e.g. 1H. An additional convenience is that 12C and 16O have no nuclear spin so these nuclei, which are common in organic molecules, do not cause splitting patterns in NMR.
31P and 19F typically have very high natural abundance, such as 1H. Moreover, 12C and 16O lack nuclear spin, so they don't produce splitting patterns in NMR; these nuclei are common in organic molecules.