Why is it that my husband does not talk about marriage only doing S*X

The babe is crying that she is tired of hearing of marriage from her guy only when
he's on top her:
"My boyfriend only proposes when we are making love.... .in the heat of a
passionate moment he says things like 'let's get married', 'marry me', 'when
do you want to get married?'
But once we are done, he doesn't mention it again ..... and I'm too shy to
bring it up. Pls what should I do?
But I think most times it is ladies who ask men all these funny questions in the
heat of the moment and guys are in a "wonderful" state that time, so they say
anything just to make sure the action doesn't stop.
But she says her boyfriend's own is too much. What do you think she should do?