A synthetic Garand stock is completely impervious to moisture. It cannot swell, shrink, or warp, all of which can, and do, adversely accuracy, and sometimes even function. They require virtually no maintenance. Since the butt stock is often hollow, the user can add weight, in the form of a cleaning kit, spare parts, and other supplies to customize the center of balance of the rifle as a whole.
They can be easily painted to suit the user, and properly bedded, the bedding job is a permanent one.
If the rules had not forbidden it, the competitive shooters who used Garands back in the day would have universally chosen syn stocks for their rifles.
Being stronger, lighter and less susceptible to cracking, it is likely that had such an alternative stock been available, Garand himself would have proposed adopting it for general issue.
There is a time and place for pretty things, nicely figured wood being among them. The Garand is a battle rifle, and does not need to be pretty to do its job.
Note to M1A4ME: the butt plate on the RamLine is removable; it's just hard to find the two, small Phillips head screws that secure it. BTDT. Replace the screws with larger-headed stainless steel screws, and use a X-Acto razor knife to open up the holes for the screws so you can get to them more easily.