Marriage is front and center in Much Ado About Nothing.
act 1, scene 1 - Claudio sets eyes on Hero + intends to marry her. (He moves fast.)
The plot thickens: there’s scheming to marry Beatrice and Benedick, to un-marry Hero and Claudio, + then to actually marry Hero and Claudio.
Marriage, though it’s the primary source of the drama, is treated like a necessary thing, otherwise the characters wouldn’t go through all the trouble it takes to get hitched.
Still, though marriage is foregone conclusion, it’s also treated lightly as a constant source of jokes.
Benedick only teases about marriage so much because it’s such an ever-present part of life. A
nother central component of marriage is the issue of deception; the butt of the marriage jokes is how everyone cheats on everyone.