But isn't tracker an ideal role for a scum to claim? It's not very common, so you make it unlikely that someone else will counter claim it. The only way to verify it is for a role to come out and claim so he can follow them, which makes them an easy target for the scum's remaining allies, either resulting in a death of a role or the doc (if there is one) being tied up.

While at the same time, it is a powerful enough role that the town would be scared to lose it.