What you observe is pretty common, especially among those using the smaller gas engines, say those less than 40cc. Many of those users are gas newbies that have yet to learn how to tune a gas engine. They are easy to spot because they are still treating their gas engines like a glow engine and attempting to tune them for every flight instead of getting the state of tune correct or close to correct and leaving it alone for the next couple years. You see them driving themselves nuts looking for boogieman with TDC "free play" and taching the engine to establish a "perfect" idle RPM, and extracting the last possible RPM from the engines at the high end. Often they have E-Z connectors securing the metal throttle linkage rod at both ends.