[throwaway346434]

If you are doing things with what is basically strings, as you find a lot of user input from web form inputs is, the advantages in having a lot of different strict types of Strings isnt huge. In these scenarios, using just basic types gets you a long way, because there is often very little business logic - route here, render that template, set these attributes.

Even a lot of JSON or XML parsing, you throw it into a parser and take what you need; if an unrelated field isnt what you expected, just move on with things rather than stop everything because the library author forgot about extension or openness possibilities (ie: an xs:any in a schema).

This attitude comes from the assumption not that types are unhelpful; just the chances we've modelled every outcome into our view of the world and gotten that right is unlikely.

When you get to complex systems with state changes to data and strict, well defined policies, rules engines, etc? Thats where dynamic languages often start adding all of that validation layer, to assert for right now you should act more like a type system and it's important - it probably has financial or security or other risks.