The important thing to realize is, what would you do, if you didn't have the call? If you didn't have call options, but you wanted to have a position in that particular stock, you would have to actually purchase it. But, having purchased the shares, you are at risk to lose up to the entire value of them-- if the company folded or something like that.
A call option reduces the potential loss, since you are at worst only out the cost of the call, and you also lose a little on the upside, since you had to pay for the call, which will certainly have some premium over buying the underlying share directly. Risk can be defined as reducing the variability of outcomes, so since calls/shorts etc. reduce potential losses and also slightly reduce potential gains, they pretty much by definition reduce risk.
It's also worth noting, that when you buy a call, the seller could also be seen as hedging the risk of price decreases while also guaranteeing that they have a buyer at a certain price. So, they may be more concerned about having cash flow at the right time, while at the same time reducing the cost of the share losing in value than they are losing the potential upside if you do exercise the option.
Shorts work in the same way but opposite direction to calls, and forwards and futures contracts are more about cash flow management: making sure you have the right amount of money in the right currency at the right time regardless of changes in the costs of raw materials or currencies. While either party may lose on the transaction due to price fluctuations, both parties stand to gain by being able to know exactly what they will get, and exactly what they will have to pay for it, so that certainty is worth something, and certainly better for some firms than leaving positions exposed. Of course you can use them for speculative purposes, and a good number of firms/people do but that's not really why they were invented.