Why did the piggy bank break up with the wallet?

This joke gets its giggle-factor from a clever bit of wordplay combined with some whimsical personification. We've got a piggy bank, the ultimate symbol of careful saving, having a relationship spat with a wallet, which is, let's face it, pretty much designed for spending. The humor lands squarely on the punchline, "You're too loose with your cash!"

That phrase "loose with your cash" is a fantastic double entendre. Literally, a wallet can indeed be a bit "loose" if it's old or overstuffed, letting money slip out. But more commonly, it's an idiom we use to describe someone who spends money freely, perhaps a little too freely for a thrifty piggy bank's liking. It's a playful jab at differing financial philosophies, all wrapped up in a silly, anthropomorphic breakup.