Full Idea
Almost any subject with any formal rigour employs some set theory.
Gist of Idea
Every attempt at formal rigour uses some set theory
Source
Volker Halbach (Axiomatic Theories of Truth [2011], 4.1)
Book Reference
Halbach,Volker: 'Axiomatic Theories of Truth' [CUP 2011], p.25
A Reaction
This is partly because mathematics is often seen as founded in set theory, and formal rigour tends to be mathematical in character.