>>10
Uh, sockets and threads are implemented in pretty much any major CL implementations (and there's quite a few of them). Whatever little differences there are between implementations, they're easily handled by thin compabitility library which provides a standard interface. I write the code once and run it everywhere. If your complaint is that it's not part of the ANSI CL standard, that's hardly an issue, since the standard isn't meant to specify every damn little library that you can think of - especially since at the time it was made, UNIX was hardly the only option and multithreading was quite experimental, so they left these things to newer version of the standard (or just to implementors).
Installing libraries(systems) so so damn easy compared to other languages, that it's hardly any work for me to add new libraries and keep my code portable.