So if I can paraphrase what I think you said, is that "all CD player/rippers in newer computers will give a perfect file copy" so there is no need to test this."
MC uses a secure ripping algorithm to confirm that the data read during a rip is correct, it just doesn't use accuraterip as part of that integrity check. There are a number of different ways to skin a cat when it comes to verifying data integrity, see:
http://wiki.hydrogenaud.io/index.php?title=Secure_ripping#What_is_Secure_Ripping.3FAccuraterip is one method, but it's not a failsafe; all accuraterip does is compare your rip to someone else's rip. If the rip in the accuraterip database contained errors, then you'll get the false positives (not likely because the database often contains multiple identical rips, but it's possible especially with obscure releases). A more common scenario is that some CDs have multiple international commercial releases that are slightly different, which can result in false positives.
MC's approach relies on re-reading data on your actual CD to ensure correct data transfer. Jim's right, modern drives are much, much better than drives from the 90's, but some error correction/detection is desirable even with modern drives for dealing with damaged discs, and JRiver's secure ripping deals well with that issue.
A case study: I had a disc that shipped with a large scratch on the outer edge, which I did not notice immediately.
I initially ripped it in Windows Media Player (before I discovered JRiver), and WMP happily ripped the disc and spit out ten files with no error messages or other commentary. When I went back and listened to the rip, the second to last track contained audible skipping, and the last track was virtually unplayable because of how much stutter/corruption was in the track.
When I used JRiver to rip the same disc, it re-read the second to last track repeatedly until it managed to get a "correct" reading, and produced a file that had no audible artifacts. For the last track, JRiver tried repeatedly to rip it, but ultimately provided an error indicating that the track was unreadable. That's when I noticed the scratch
When you're ripping a large collection, you want to know when something went wrong with the rip because you may not test each individual track as you rip it, and JRiver's secure ripping has been more than adequate to alert me when a disc has problems. Nine times out of ten, JRiver can get a solid read by re-reading, and the rest of the time, it's good to know when a disc is damaged.