Think of it this way, several M14s were brought back into service for DM use in A'stan. Many companies have developed .308 AR rifles for use. Canada uses the AR10, Brits use the LMT, we are using the M14 and quite a few Scar 17S
The reason we (the army) brought the M-14 back, is honestly because we're stupid.
It was because we decided to issue a red dot sight, and not a magnified optic, so as soon as we hit the mountain warfare of A-stan, we were lacking the ability to make hits at extended ranges. Guys were putting the dot on the target pulling the trigger and then complaining about the lack of 5.56's ability to kill. Instead it was a lack of ARM (advanced rifle marksmenship) simply put, we weren't hitting our enemys.
But, we had a bunch of old dinosaurs that had grown up with the M-14, and as soon as we had any issues, it was "5.56 sucks, gimme a 7.62" and we paraded a bunch out, and fielded them as a stop gap, with a magnified optic, and people went nuts, because oh my god, we can make hits at extended ranges now. They were also phased out with free floated, scoped M-16's in the DMR role.
Notice, you never saw alot of love from the Marines for the M-14. But nearly every single Marine you ever saw, was toting a M16 with a RCO. Funny thing.
Enter the SAM-R, DMR and SPR rifles. All 5.56, all designed to fill the role the M-14 was used in, and none of them in 7.62....
It was a fine rifle, for its time. But much of the love for the M-14 is from the myth of the weapon, and not based in actual first hand use. Its not as accurate or robust as people make it out to be. Much like the AK's often overstated by people who don't like the AR. Talk to the 101st guys who were carrying the brunt of them, and the shooters who've run them as a DMR rifle, and they don't really sing the praises of the extra hunk of gun they had to carry around for a role that the guy on the ground never really asked for.
Also, a DMR, or SAM-R rifle will shoot rings around an M-14. Even the Crane/SEI M-14's aren't anything to write home about.