And two more reasons not to say ‘why don’t you have kids’ or ‘you’ll want them later’ are 1) having a genetic illness (either recessive or not) and don’t want to pass it on* and 2) really wanting kids and not able to have them**.
*yes, I know someone like this. She and her partner adopted a child.
**cause everyone enjoys having lemon juice poured on a paper cut, or on an open, bleeding wound, so yeah, go ahead and ask.