The "exit" flag doesn't mean what you would expect it to mean. The reason such a node won't get much traffic is that Tor speculatively builds circuits at startup on the assumption they'll be used for web browsing. Thus if you don't exit web traffic you won't get much in the way of traffic at least not until bitcoinj based wallets start shipping Tor mode.

There's a perfectly reasonable explanation for why someone would run such a node. In fact I run a Tor exit that only allows port 8333 too: it's a way to contribute exit bandwidth without much risk of getting raided by the cops.