Choosing one's operating system is not merely about possibility, it's about productivity.
If a system is simpler, and has fewer and more robust APIs that work for more attached systems, then in theory at least it will be less work to program for, the programs will require less maintenance, and tasks will be accomplished with less friction.
The question, of course, is whether this improvement is sufficient to warrant the many headaches of changing operating systems; in general, it isn't, which is why Plan 9 failed.
Sure. So, what's the application that can be built more easily, with less friction, on Plan 9? I'll make it easy; what's the application that's easier to build on Plan 9 than on Win32?
> There is no ftp(1) command under Plan 9. Instead there is an ftpfs fileserver, and each FTP connection looks like a file system mount.
So, an application which needs access to files on another system can make one call to ftpfs, then return to using normal system calls to read and write files. With ftp, you would have to write an application to deal with the ftp client's api instead.
Presumably this advantage wasn't enough to get Plan 9 lots of users.
I don't even think it's an advantage to application developers. Some of the ideas behind application-filesystems have been discredited (for some of the same reasons as RPC was discredited), but more than that, it's just not that much more convenient for the application developer.
In every programming environment I can think of, you're only ever a library call away from FTP anyways.
I think it is an advantage to application developers. A lot of good ideas die because the programmer has to write 900 lines of cruft wrapper code to experiment with a 100 line cool idea, and the programmer never makes it through the 900 lines.
If you can mount web pages as a file system, then you can write a web search indexer in a few tiny lines of code. In fact, you can focus on making simply index-search functionality, and ignore whether it is a web search engine or desktop search engine.
Alternatively, you can use curl or some other library, and you can still get the job done. But you end up thinking a lot more about interface stuff to write applications, and computers end up having huge amounts of duplicate code on them -- curl, the code in various browsers, just numerous different implementations of client http all over the place, and many of them incomplete or buggy.
If a system is simpler, and has fewer and more robust APIs that work for more attached systems, then in theory at least it will be less work to program for, the programs will require less maintenance, and tasks will be accomplished with less friction.
The question, of course, is whether this improvement is sufficient to warrant the many headaches of changing operating systems; in general, it isn't, which is why Plan 9 failed.