It seems the norm these days is for installers/setup programs to request that you close all open applications before initiating the install process for a piece of new software. I used to obediently follow these directions without fail, even though it could sometimes be frustrating having to close open documents and stop working on things just to get a new, seemingly unrelated application installed. Then at some point I simply stopped bothering. Nowadays if I have a lot of stuff going on I might even run multiple installers at the same time; I can't even recall a time it has ever posed a problem.

Why do setup programs even make this request in the first place, then, when it appears to be unnecessary? Is this just to simplify troubleshooting for companies' support people? Has anyone else ever run into problems as a result of trying to install an app while other apps were open?