Just like there's minimal risk involved in skilling or training-like services. How does me leveling someone from 1-25 firemaking show I'm trusted? Oh wait, it doesn't.
No risk involved, just time... like all the torso, firecape, skilling, and training services. How is there risk at all involved when a person can recover their account back at any time. The only possible thing that could go wrong is that they level the wrong skill. You're honestly telling me that a newbie who raises someone's level from 1 to 20 for free deserves a vouch, yet someone who spends hours on GFX for someone deserves nothing? You're trusting the person not to resell the GFX they sold you. You're trusting that person to actually give you the GFX in the end and not run.
It's no different than selling gp and using a MM. If you use a MM, the person buying the GP has ABSOLUTELY NO RISK PERIOD, yet he or she can still receive a vouch. Most of the people's logic on here is seriously flawed.
You're right, because the guy who has 50 vouches for doing free training services for people under level 30 should really be trusted... You've got to be kidding me. You allow people to vouch for practically anything, yet not GFX?