When I wash the windows there are no streaks but they don't sparkle like my window cleaner's windows. What did he do that I don't.

This is a window cleaner's trick.  If he has extra time he probably cleaned the inside of the glass with either 000 or 0000 steel wool.  This method removes micro-abrasions in the glass without scratching the glass.  In fact if we're cleaning french windows and doors, this is how we clean the inside - because the panels are so small.

This method isn't all that effective for large panes of glass because of the surface area that needs to be cleaned.  Also it is more physical work to use steel wool rather than a sqeegee.  But it surely does a great job.  Also we don't normally use it outside because of the dirt that's on the window.  Scrubbing dirt with steel wool could scratch the glass.  Cleaning it first the normal way, and then using steel wool is very time consuming.  Thus most window cleaners don't do it on the outside.