Sure, discipline can prevent some errors. But it's always possible to run into wrong type assumptions, and I'd say type coercion and null/undefined access make up a fairly large percentage of non-logic errors. You can entirely prevent those using Typescript, which is why it's so useful.

Static type analysis is always a good idea if you're writing more than a couple lines. IMO Python is the worst offender with its kwargs etc. - discoverability and testability is just so bad if you're following common Python idioms.