Some things to consider:
1 As a consultant, there is no way I will sign off (read: pay) a vendor for any work not fully tested. This is especially true for CAT6. It has been true for CAT5e. Of course CAT5 and lower are no longer compliant to Standards so don't bring the product to the Project.
2 If the system has been warrantied ("20 yr"

by a manufacturer you are required to fully test and make sure the documentation is added to the site. If you are not certified by the manufacturer you will probably void any warranty on what you installed/touched.
3 I was not aware that modern testers that can do wire map reporting will not also do a full test automatically. It only takes a few seconds.
4 In these days of CYA, full testing and presentation of documentation is both useful and can be a sales tool.
5 If there is not a consultant involved or the Owner is naive, it is your responsibility (read: ethical) and opportunity (read: sales) to educate the Owner that his expensive (in his mind) installation will be compliant and the best value for his precious greenbacks.
6 Testing is the only way to know you or your staff are doing quality work. It is also the only way for your customers to know that you do quality work. How can they say you did a great job and promote your business if they don't have something other than electrons and ether to see and touch?
7 As an industry, cable folks should strive for the highest common denominator rather than the lowest. This is a real serious issue!
8 Look at the distributors' (Graybar & Anixter) certifications - there are some manufacturers who can't consistently hit the requirements and as a result aren't certified (set aside the politics of this issue). There is definite proof in the pudding of all manufacturers that every inch of cable and every I/O does not meet spec -- you never know until you test.
9 Especially for CAT6, it takes very little to bust a successful installation. That extra jerk on a stuck cable, that bind turned into a kink (even when "straightened" out) or that uncomfortable reach to terminate in a poorly lit TR or WA leaves you and the Owner at risk for failure.
10 Cable installation is one of many possible reasons for poor bottom line performance for the Owner -- it usually is their stuff -- test to remain profitable and your halo held high.