What is the purpose of std::stringstream? [on hold]

Before the C++11 methods to_string(), stod(), etc. were available, stringstream's stream extraction and insertion methods provided a somewhat convenient method for converting between strings containing numerical representations and actual numerical variables.

Now that to_string(), stod(), etc. are available, what other uses are there for stringstream? (I'm guessing that I'm missing the fundamental point of stringstream.)