Other than being dirt cheap ?
The low price of them is a major part of the attraction. But they are as reliable as anything man-made can be.
they are one of the most obtainable historic firearms. they were produced to serve a russian army that was one of the few immovable objects or WW2. They are simple, easy to build east to maintain, easy to shoot. any Russian citizen could be conscripted into the army any be able to fire bullets at the enemy with reasonable accuracy. When looking to collect historic firearms, they are the most obvious starting point, because of their availability, price, available ammo, and ease of use.
They also make a good starting hunting rifle, they are nearly indestructible, and if you manage to destroy it anyway, they are easy and cheap to replace.
reliable, cheap and a piece of history...many Russians probably died holding each one of those mosins
People who know how to shoot can get good accuracy out of a Mosin, I