Whilst there are difference, I'm not sure it's really true that the underlying always exists for futures. The main difference between the two is that futures ar

Whilst there are difference, I'm not sure it's really true that the underlying always exists for futures. The main difference between the two is that futures are standardised contracts traded on an exchange and typically subject to daily margining/price settlement which has some impact on the behaviour of their price over time. Futures are useful to a broader group of people precisely because they don't need to involve physical settlement. Many people use commodity futures to hedge exposures to the price of assets which are not the underlying in the future but where there is a relatively predictable relationship between the two prices. Others use them to speculate on prices despite having no ability to deliver or take delivery of the underlying. Some contracts are even purely cash-settled. (Edit: made clear that it was the point that futures always involve an underlying which already exists I disagreed with.)