If we instead consider staking rewards to be payment for services, we will look at §61(a)(1), which says that compensation for services is included in gross income. Generally speaking, compensation for services is paid in cash (i.e. a paycheck). However, staking rewards are paid in crypto. No matter, §83(a) tells us that property transferred in connection with the performance of services should be included in income at its fair market value, less any amount paid.