Comfort, speed, preference, flexibility, lack of benefit on web projects where all data is by default a string, your ORM has already mapped the types directly in the database and will transform everything automatically without repeat definition, you're dealing with a lot of JSON API calls that may change where you don't _need_ all of the data so being forced into a situation of strictly typing 3rd party nested substructures can created a lot of wasted time...

Just off the top of my head. To each their own.

I like Ruby! Ruby has types. They just aren't enforced by a compiler.