A huge fraction of tor usage is illegal. Drugs, and other illicit sales mostly. Some pornography. None of this is relevant to an exit node operator because the servers for these people are using hidden services, and as such their traffic never exits the for network, and never passes through an exit node.

The illegitimate uses of tor that require exiting the network are fairly limited, and tor isn't great since the list of exit nodes is public, and blocked many places. Mostly those users are trying to bypass a firewall or browse anonymously for one of the reasons that for advocates claim.