A: Many Reasons!

longer answer? okay...

Why isn't an automobile one-size-fits-all? Or a home theater? It has to do with very human concepts like:

• Comfort Level
• Software Used
• Skill Level
• Technology Understanding
• Overall Function of the PC
• PC Hardware Specs

I'm sure there are more - but the idea is kind of like this:

If you use your PC for chatting and socializing, and you have a current generation Core i7 CPU with 4GB of ram - your software environment can and should look a LOT different than someone that ONLY uses the computer for homework, has a 4 year old Pentium M CPU and 1GB of ram.

The technical reason - the first case you could have a few instant messaging applications installed, social toolbars, favorites synchronization, and multiple web browsers open at the same time and this could be normal and stable for a current generation computer.

In the later case, a computer used only for homework, having these programs installed and running all the time would have a HUGE impact on performance.  No software PC cleaner will ever be able to figure that out and optimize your computer for you.

Sounds like a lot to try to understand?

You don't have to.. Here is the cheatsheet

1. The newer and faster the CPU and more Memory you have - the more stuff you can put on the PC without a second thought. Literally, a current gen PC won't need a tune-up for quite a while.
2. The older and more 'classic' your PC - the longer the life you want to get out of it, the more you should keep an eye on the extra stuff installed and running at the same time.
3. When your machine gets over 1 year old - really think about what Antivirus Software you want to use, think about upgrading all your web browsers, and doing a set of Windows Updates if you have been putting them off.

 Check out a software tune-up by Dr PC Fix - available Online now