I agree that the body produces enough natural lubrication if the lovers carry out enough foreplay. I can honestly say that over many years with many lovers I’ve only had to use lube with one partner and that was an age/menopause thing. Yes sometimes it can be tight to enter at first, but for the male lover that should be a clue that you have some more work to do. Maybe more oral is required, or clitoral massage, or slow finger technique. If the male is sensitive to his partner he should know what is required before penetration. If anal then that is different, mostly, unless the lady in question is a gusher and that naturally lubricates so much that the male slips into the wrong entrance by default. That also happened and was very enjoyable by both, but that is an exception to the rule. Sensitivity is the answer to this question. If the male is a sensitive, sensual lover on balance I would say you should not need lube. If however, they are a crash bang merchant only interested in their own release and an ass in more ways than one, then be prepared.