Yes, you need. Otherwise there's always foldinghome that requires your pc resources without economic incentives. But that's not a blockchain and there's no money at stake. Any blockchain that attempts to secure any value must be incentivised.
I think this is possible because its part of a circulation. Encrypting every transactins might be easy but after many transactions everyday. The blockchain server might need to another server or more manning to handle every transactions. Because there is a big chance that "hardfork might happened if the incentives is just the same. As the growing price of btc if bursting and many more investors are comming in. And blockchain does not only transac btc but also other altcoins.
