These glands are heavily concentrated in the armpits and genitals.
Well… since they can’t reach the armpits, so crotch it is…”.
Dogs cannot speak so they have their own ways.
Your dog is just trying to know you, but if you’re embarrassed with this innate behaviour,
you can redirect it by training your dog; giving treats and saying basic commands such as sit, stay, etc.
Their sniffing is equivalent to asking your name, where you live, as well as shaking hands.
As non-verbal species, this is their way.