“If you could pass the salt, that would be awesome” is better than “Pass the salt” some times. “Would you like to go out for a drink with me?” is better than “Do you want to have sex with me?” at other times.
We speak in such euphemisms because, Steven Pinker explains, language is meant to do two things at once. First it needs to convey content. Second it helps to maintain a social relationship.
Using euphemism, one party can indirectly convey content when making a request and the other party can accept or decline requests, while still maintaining the social relationship. Both parties understand without directly acknowledging the said change in relationship.