Both the giver and receiver gain physical and emotional sexual pleasure.
STDs can still be transmitted.
Only performing fully dressed oral sex on a stranger or friend does not dissuade the anger and pain experienced by your wife-girlfriend/husband-boyfriend whom you cheat on while performing the supposed "non-sex" act.
It is sex. I think the "naive" comes in by thinking such a distinction matters or is necessary. Is the purpose of such an idea to avoid guilt? Or set a legal precedence? The idea is just dumb.