I am in a small school also, and i would say that about half my students use their lockers regularly and the other half never use them. The lockers provide secure storage for things not needed until later in the day, which is a huge boost for students involved in sports, musical instrument lessons, or other after school activities.
I sometimes ask students to weight their backpacks and consider using their lockers to lower the amount of weight they are hauling; I am concerned about their physical health from carrying such loads, especially since most only use one shoulder strap.
One really valuable thing that lockers do, but that no one ever considers, is to separate clothing and keep it from touching. Having students hang their coats on hooks on a common wall is actually a terrible idea, as it allows lice, bedbugs, etc. free travel from one item of clothing to the next. In many states, health codes are being implemented setting minimum distances between coat hooks or requiring vertical barriers between them so the clothing doesn't touch.