How is that cargo-culting? GP's comment doesn't even seem to come close to the meaning of cargo-culting. And yes, type definitions in my projects account for a good percentage, anywhere from 5-25% of each file, if you take into account all the interfaces, parameter definitions, class types... So that's removing 5-25% of your minified JS bundle, and if we're talking a 4mb bundle, that could be 1mb of type information, completely useless at runtime. If you needed to map that type information to your source code, this is what source maps are for!