Most futures tend to be cash settled in general in fact e.g. Eurodollar futures (the most liquid contract in the world) which have an underlying tied to 3 month LIBOR (i.e. effectively a bank deposit rate - very liquid indeed) are cash settled. And even for contracts which specify physical delivery (eg most commodities), most open interest is either closed out completely (or rolled to the next contract) prior to expiry day which means no physical settlement takes place.

There are a few reasons for this but broadly it comes down to the fact that cash settled contracts are more attractive to a broader set of investors (which means more volume and thus more income for the exchange which sets the contract terms). For example, cash settlement is more useful to investors who wish to hedge something which is close to or correlated with, but not the same as, the underlying. Hence the popularity of Eurodollar futures. This is even the case with many commodities (how many people actually want to take or make delivery at the specified delivery point?)

Playing against this is the fact that if the underlying market is less transparent (as is the case for many commodities) then physical delivery might be needed to ensure that meaningful arbitrage can take place to ensure confidence in the market (if arbitrageurs would otherwise stay away from the market then this would reduce liquidity of the futures contract - to the disbenefit of the exchange).