For the same reason Navy match team shooters were still using Glenn Nelsons supurb match Garands into the late 1980s and early '90s, then finally switched to the match M16A2NM [and Mark Twelve Mod X, but that's another story]
If you shoot the NM course four or five, sometimes six times a day, your scores will be appreciably lower the last time or two you go at it. With the lighter and lesser-recoiling 5,56mm, that's less the case, though shooter fatigue and burnout remains a problem to be overcome.
Now when I can pull off four runs a day, I shoot the first one with a Garand, the second with an M14M, and the last two with an M16 variant. I've even been to an Appleseed shoot, where a kindly and well-intentioned instructor somewhere between 25 and 30 years of age did his best to *teach me how to shoot* the M16A1 I'd brought along that day. Ho ho ho.
>>I’ve even been to an Appleseed shoot, where a kindly and well-intentioned instructor somewhere between 25 and 30 years of age did his best to *teach me how to shoot* the M16A1 I’d brought along that day. Ho ho ho. <<
Some young folks are just friendly and helpful towards us older folks. Just doin what Mommy taught them to do.