What is the origin of the idiom "cupboard love" and when to use it?

The idiom "cupboard love" is thought to have originated in the 18th century, when it was used to describe the love that a husband and wife had for each other when they were in need of food or shelter. The phrase is based on the idea that people who are in need of food or shelter are more likely to love each other than people who are not in need. It is now used in a more general sense to describe any type of love that is based on need or convenience rather than on feelings.