Why did the US government issue 22 LR sniper rifles durning World War 1?

They did not. However, during WW 2, the government purchased .22 TARGET rifles to be used to train service members in basic rifle marksmanship. Training was mainly for people that would not be expected to use the M1 Rifle on a regular basis- such as Navy, Air Corps, Women's Army Corps. .22 rimfire ammo and the rifles to shoot it were less expensive than the M1 Garand. I have one of those rifles in my collection (a Mossberg 44US)- and while they are very accurate, their maximum effective range is about 100 yards- hardly a sniper rifle.