"...Something to do with the mechanics of it..." It's the design, not the mechanics. The M1 was made to shoot with the 8 round enbloc clip and nothing else. This was one of the major complaints. No 'topping up the mag'.
The 5 round clips are very much commercial things and were made to allow hunters to use the rifle where more than 8 rounds is illegal, Stateside. They run $5.50US each from Gunparts. You don't need 'em here unless your Provincial hunting regs says no more than 5 rounds in a rifle.
There are States that don't allow centrefire rifles for deer hunting, States that don't allow more than 5 rounds in the rifle for hunting anything and States that don't allow semi-autos period. Plus some that specifically prohibit some centrefire cartridges.
Your SKS is fine for close range deer sized game with a pinned mag and the right hunting ammo. Even though the sights are poor. Just remember a Warsaw Pact issued SKS will have a .311" diameter barrel. .308" bulleted ammo(most American made hunting ammo unless otherwise stated uses this diameter bullet) won't shoot well out of a .311" diameter barrel. It's the wrong bullet.