This is because of the architecture.
The major reason for this behavior is that Linux doesn't lock executed files and libraries, which allows direct replacement of those files and does only require the applications to restart. For installations is the reason the package-management-systems, while in Windows every program installs all needed libraries (even if they're already installed, but when they are in use they are locked, which needs a restart to clear the situation) in Linux an application only references the needed packages which are installed once (and never again), reducing the overhead.