They are the only way for a regular individual to emit their own bonds or better yet a promissory note.
Simply give your counterparty a post-dated cheque, if you have a good reputation you they'd give you the stuff immediately , and you have X days to find the money to put in your bank acount to satisfy their claim.
In countries where a bounced cheque means jail time such as Bahrain and Kuwait a post-dated cheque is essentially the same as money provided that the beneficiary informations have NOT been filled out (it's the bearer who fills the stuff out)
It's essentially a form of P2P lending which should not go away until we can do the same with bank wires (meaning setting up a bank wire transaction and give proof to our counterparty that we did so and that we cannot modify it).
EDIT: Now all the crypto-bros will come out of the woodwork with smart contracts....to which I reply: ok , do it, don't just talk about it
Checks have the advantage of no overhead. I don't have to pay transaction costs. That's not enormous, and the checks themselves require handling that costs my time, but it means that in a lot of cases it's just easier to do the thing that we already know how to do.
(Checks are better because a money order basically required a trip to the store for each one.)