Why is networking so hard?

Networking has been around for more than 50 years, so why doesn't it work? Why is it so hard? Shouldn't it just do what it is supposed to? I can't see why this is so difficult.

I just wanted to transfer a file from my Mac running OS X Lion to my Windows 7 PC. Both were on the same network, but I couldn't see the Windows computer from my Mac even though the Windows PC was set up to share its Public folder. I tried Go, Network in Finder and there was nothing.

I thought I'd try Go, Connect to server and then use smb://192.168.1.64 or whatever the IP address is. The trouble is I didn't know what the IP address of the Windows PC was. My Mac was downstairs so I had to run up the stairs and go to my Windows computer, click through three or four dialogs to find its IP address, run back downstairs to my Mac and type them in. The Mac then connected to the PC and I could transfer the file.

Why on earth did I have to do all that running up and down stairs just to connect one computer to another on the same network? Why did I have to look up IP addresses? I know this simple task of connecting one computer to another to transfer a file would have defeated some people because not everyone knows how to find out the IP address of their computer, just as some people can drive a car, but haven't a clue how the engine works.

I can understand (but not agree) with Windows PCs and Macs not talking to each other. There is probably little incentive for the companies to support each other's computers, but I also have two PCs running Windows that can't talk to each other. One is running XP and the other is running 7. Why can't one PC connect to another PC's shared folder? I'm fairly knowledgable and part of my job is tech support solving people's computer problems and I can't solve this one. What chance has an ordinary user got?

Why oh why is networking so hard?