All data has SOME structural metainformation that can be captured in a type. If you are importing a CSV file, you know -- at a minimum -- that it's a CSV and can be parsed as a set of tuples of variants (or else there's something really wrong with the input and an exception continuation should be invoked to handle it). From there you can do analysis on the data to further refine its type.

But ALL data is typed, and encoding its type early in the code that processes it makes your assumptions clear and compiler-enforceable.

You're right that a typed approach to handling arbitrary input data is not right for a library like Pandas. It's a fundamentally different approach than the one Pandas takes, but it's no less valid and brings with it certain advantages.