Same reason we don't say "she loves her own husband" to avoid mean she loves a husband of another woman.
It is a common meaning that someone loves his own parent, even if we don't emphasis this. And this language details leave room for jokes and pranks.
Because the rule that says there are no definitive articles (il, la) before a singular family member extends also to marito and moglie
Can someone tell me why the possessive adjective ('suo') is not preceded by the definite article in this sentence? The general rule seems to be that the possessives are always preceded by definite articles - why not here? Thanks.
Because it's a family member. That is an exception to the rule. (An exception to the exception is that you DO use the definite article if you are referring to multiple family members. So "mio fratello", but "i miei fratelli".)
Duolingo, I must remind you that 'Lei ama' means 'you love' (formal) as well as 'she loves'