Consider the following scenario:

You have a Toilet object with a method flush.

  var toilet = house.getToilet();
  toilet.flush();

Now you find out that updating Toilet objects is somehow expensive and decide to wrap it into a Cache<Toilet>. Unfortunately, Cache also has a flush method, so there will be no compile time error, but functionality is broken now.

I agree this problem would also occur when using chained calls (house.getToiled().flush()), but explicit types could cover at least some of the cases.