As a person who has been writing JS for a very long time, and was building SPAs before the term existed...

It all comes down to return on investment. The arguments I always hear in favor of TS are solutions to problems I've never had, at the expense of writing more code to do the same amount of work.

It's the same for people who tell me that they think everything should be tested then show me the tests they spent the last 40 hours working on, which I can quickly see are extremely brittle and unlikely to ever show any ROI. You will never be able to test every scenario, increasing the amount of things you test arbitrarily just increases the cost of building and maintaining your software. Each test you add should be something worth building and maintaining.

Excess code that isn't providing value is far more detrimental than not having a few extra tests or type safety.