Because to provide you the software for "free" they monetise it in other ways.
Usually, this means selling you out to third parties (who will then aggressively market their wares to you) or bundling unwanted extras to serve you advertising and turn your computer into their advertising medium.
As a general rule, if I see a program that has words like "boost" or "optimise" (or any variant thereof) in their names or descriptions, I avoid like the plague. The ONLY exception is Ccleaner which calls itself an optimiser but is worth having around.
Another trick often pulled by driver update programs is to scan your system and then tell you that you have some 50,000 drivers that need updating. Click here to update!!! So you do .... and get greeted by a paywall
EDIT: Another thought about constant driver updates. The version they want you to update to, the latest and greatest version, is supposed to fix all your problems.
The version you currently have was once the latest and greatest, and was the recommended go-to version.
So you update to the current L&G version which invariably contains stability patches, bugfixes, improvements and new features.
Guess what? These code changes can also contain bugs, memory leaks, etc.
So now you have a version that leaks memory in other ways to what your old one did. It's just that nobody has discovered them yet, and they didn't come out in testing.
Wait for it .....
...For a few months ...
...Another new version!! Update to the L&G version to get the latest stability patches, bugfixes, improvements and new features!
And so on.
I'm not saying hat you should stay on prehistoric drivers, just that the latest versions may not be all they are cracked up to be.
Because of this, I'll typically wait until they appear as part of a regular Windows Update and deploy them that way.
Edited by Angoid, 20 April 2017 - 11:14 AM.