In a lot of cases, so far in my career, using iostream's and sstreams and fstreams in C++ is absolutely fine because most of the programs time isn't even spent

In a lot of cases, so far in my career, using iostream's and sstreams and fstreams in C++ is absolutely fine because most of the programs time isn't even spent there, it is spent in the data crunching algorithms. I am a real world C++ programmer, I can only claim about 5 years experience though, and I use iostream. So yes, your data is anecdotal, so is mine, and we are both complete opposites.