Why does a jailbroken iPhone always ask to restart Springboard after installing a new app? I just jailbroke my iPhone and it went well. 

Why does a jailbroken iPhone always ask to restart springboard everytime an app is installed from Cydia? It's so annoying. It's like installing an app on a Mac and having to reboot the machine. I jailbroke using redsnow.

Any answers?
It doesn't always - only when the new app directly affects the interface. So when you install command-line only functionality there is no need to respring - at the other end of the scale you would also need to respring every time you change a theme in, say, winterboard, even though you are not installing a new app.  

The reason for this behaviour at both ends of this spectrum is that none of the jailbreak 'tweaks' can affect the springboard while it's running - they have to change the filed copy and then restart with a new version of springboard...