There is no point to use MS Windows or similar MS applications, because of only one reason:
- There is no source code to be available.
Sorry, but that's just an extremely narrow minded and unrealistic view of the world. Things don't work this way. In fact, I can't help get the impression that you're borderline trolling right now.
Riddle me this: what advantage does the availability of the source code provide for an end user who isn't a programmer and has never ever compiled any piece of source code in their entire life? Simple answer is
absolutely nothing.
Most people who enjoy open source software do so for one very simplistic reason: because it's free. It doesn't cost them any money to obtain it and they can use it. But this has
nothing to do with the availability of the source. Before open source got more mainstream we used to have freeware (and shareware): software which was made available free of charge, which could often be used fully free of charge (sometimes within a few limitations) and which usually was closed source. And no one couldn't care less.
Even so... fact of the matter is that there is plenty of commercial software out there for which there simply isn't a suitable or usable open source counterpart.
A very good example of this would be
Max; a visual programming language fully aimed at providing multimedia based solutions. The fun part is that the project eventually split between an open source variant called Pure Data and a commercial project called Max/MSP.
Both projects still exist today and both definitely have their place.
However... Pure Data, although still a very impressive project, doesn't even come close anymore to the rich feature set which
Max provides. Both links point to their respective websites, you'll see.
So what do you think which product would be preferred by an audio or multimedia engineer? Better yet: do you really think they'd care about the availability of the source code? Of course they don't. What they care for is to know if the product will support their hardware, if they can develop their own programs to be used in their setups, if the product supports the latest (MIDI/ASIO) standards, stuff like that.
There are dozens of examples in which closed source is basically blowing the open source solutions out of the water. And there are plenty of people who happily pay money for that as well. They don't care about source code and all of that political stuff, they care about getting a tool to help them get a job done and for that they pick that tool which works best for them.
Sometimes that can be an open source solution, sure enough, but in many professional markets closed source solutions still reign supreme. And for very good reasons.