The trouble is just volume and time, even just reading through the description and "proof it works" would take a few minutes, and if you're getting 10s of these a day it can easily eat up time to find the ones worth reviewing. (and these volunteers are working in their free time after a normal work day, so wasting 15 or 30 minutes out of the volunteers one or two hours of work is throwing away a lot of time.

Plus, when volunteering is annoying the volunteers stop showing up which kills projects