Why don't more aliens extract "samples" the natural way?

So I just watched this one video on YouTube about the abduction encounter of Antonio Vilas Boas and it got me thinking, how come in a lot of alleged encounters, the aliens seem to go about extracting sperm or eggs in a cold clinical manner with little regard for the person their extracting them from? Like a lot of reports say that they often extract it painfully, and not to sound crass or anything but if these beings are technology advanced enough to travel the stars, shouldn't they just be a...