There are eight reasons to insist on all matching numbers on a surplus firearm:
1.) Personal satisfaction and even a bit of snob appeal.
2.) Higher resale value
3.) Maybe a bit better accuracy and function.
4.) You enjoy your hobby and want to make it pay off a bit better in the end.
5.) You have the money to purchase it and the time to spend looking for one.
6.) Superior knowledge of warfare, great power conflicts, wars, shadow wars, proxy wars, and military ordnance policies and practices that mandate that no issued weapon was ever worn out, broken, captured, surrendered, rebarreled, rechambered, furnished to any other country or issued to more than one military, or refinished in any way.
7.) The ability to discern instantly if numbered parts have been faked.
8.) The ability to spend hundreds of dollars more on a weapon because the floorplate matches the buttplate.
The first 5 reasons are the only ones that count. Other than that, collect and shoot what you want to and enjoy each and every one of them, matching or not.
They are all historical artifacts of an era now gone, when the armies of the entire world faced each other with a cumbersome, slow, bolt action, open sighted, magazine rifle with five or ten rounds in it. Frankly, it's a wonder they have not all been melted down for scrap value by the nations that designed and produced them. Instead, they rebuilt them as carefully as they could and brought them to the great American marketplace, where our freedom to own such rifles and the wealth to purchase them keeps them intact and functioning for a second century.
Go ahead and buy a bunch of them, put them away for your grandchildren, and their grandchildren. Let the snobs cavil about their collection of stamped numbers and how valuable it is. The rest of us can put a little bit of our freedom in storage for the next generation to keep and enjoy.