Stuff like this is always kind of bizarre because it lacks context. If two untrained people are fighting in a life and death situation, then of course they should resort to whatever they can such as eye raking, targeting the genitals, biting, etc
However, this is often presented in a fashion that belittles trained martial combat, which just makes no sense. There's always going to be some smart ass at a kickboxing class that says, "well, I could just kick you in the groin", well, how? If there's a large skill gap between us, especially the vast one between a trained (ie someone who regularly spars / fights) and untrained person, you're probably never going to land a single strike.
Now lets take that a bit further - you're already probably not going to land a single strike, or at the very least anything effectual, why would you be able to pinpoint target something as particular as the groin or eyes? You're already incapable of landing a clean blow to the head, but you're going to somehow gouge my eye with laser accuracy? You're not going to land a leg kick, but you're going to blast my testicles? No, I don't think so.
It is however a sort of inverse bellcurve. Biting and targeting vital areas will help the untrained, fall off in the depiction I previously stated, but then with two trained people it becomes somewhat useful again. However, this isn't the movies - if you're training for self defense, it's best to just train like a fighter. The chances of you getting into an altercation with another trained individual is really rather slim. To get that training though you're going to have to spar, a fair amount really, and I don't think anyone is lining up to spar with the guy that wants to bite and attempt ripping off your dick.