What you are describing isn't a futures contract, but rather a form of gambling. The first example you gave, where I agree to trade you 6 barrels of oil on September first for 1 bitcoin, is a futures contract. Assuming we don't choose to exchange cash instead, you will get your 6 barrels of oil and I will get my one bitcoin.
The second example, what difficulty will be on September first, isn't a contract at all, nothing is being exchanged. It is simply a bet on a future life event. Any gambling house would be well equipped to lay odds and accept wagers on the event.
A cash-settled future is a bet, but the idea is here to avoid the use of an intermediary and counterparty risk.
A bet such as this can be used to hedge exposure, so isn't necessarily gambling.