Streams clamp everything in them to O(n). That's a problem in some cases; for example, your NASDAQ feed dumper probably has some kind of database inside itself

Streams clamp everything in them to O(n). That's a problem in some cases; for example, your NASDAQ feed dumper probably has some kind of database inside itself that lets it run filters in massively sublinear time, and making it linear would be a significant performance hit. However, there are an equal number of tasks that are not sublinear. Some of them are also very common and important sysadmin-y things. Iterate through a directory applying some operation to every file. Slurp a file and look for a particular chunk of bits. And so on. For those sysadmins, a little structure in their stream can make their job a lot easier. It'd be like the difference between assembly and C: all of a sudden things have names.