Technical,
It's amazing how many people forget that a lot of the info for a lot of programs is in the registry. Removing the program alone, doesn't read the new info into your system.
The computer still has the same old registry info in memory till the system is rebooted.
Also remember that some hardware installations require a complete shutdown and restart in order for the system to find the new hardware...
I know it's a royal pain to reboot but, there are times it becomes a critical operation.