You are right, for many IoT applications it is not necessary to have a currency, we will indeed support even "purely blockchain" solutions like Hyperledger.

The advantage of having a natural and secure way of exchanging currency between physical devices should not be underestimated though. It is something far from trivial with a normal IoT device and can enable many interesting use cases. For instance instead of paying in advance for the shipping cost of an item bought online, you could put the money into a smart contract and automatically pay when the goods arrive together with an IoT sensor which monitored the shipping. The smart contract could specify that if certain conditions are not satisfied (for instance temperature over a certain range, time delays, shocks, too much humidity) a discount or complete refund should immediately apply.