Forgive me if this may seem a stupid question, but I've yet to figure out the point of a handthrottle. If anyone knows the reasoning, any explanation would be appreciated. Thanks.

One occasion where you it would be useful is on a steep climb and a stall happens. Having one foot on the brake to stop you sliding back, the other foot holding in the clutch while restaring the engine, you can used the hand throttle to pick the revs up and letting the clutch bite without taking your foot off the brake.

Dave.

Makes sense. Ive been in that situation many times. Usually compensate by laying down some rubber/ rolling backwards and losing ground. Thanks for explaining this rather "common sense" setup to me. Maybe I'll have to hook one up for my own use (the bicycle shifter method). Thanks again for the input.

A hand throttle has many uses. Many include bringing the RPMs up so that the alternator will put out more amps. If you have an on board welder, you use it to control the power output. For engine driven air pumps such as a York, you can increase the CFM to inflate tires quicker or run air tools. When using a winch or many lights while parked, extra rpms will help your battery from being drained faster than it can be charged. They also work well when you are geared very low and want some extra crawl speed.
I prefer the electronic hand throttle as it is more precise but there are many manual styles that work just as well.

its called go to the bike shop and get a 3.00 cable, a 3.00 derailer shifter and some crimps and do it up. works great for me and has saved me once already.. gotta learn to use it though, if you freak on a hill climb it can do more harm than you intend.

like said you can use it to set the rpms while using an on board welder or on board air set up.
For the rest it's just real helpful while off roading a stick shift -> less bouncing, you can give it gas already while you got your foot on the brake and clutch (even though bypassing the clutch interlock is better ).

Mine broke last year at the Chili Challenge with still a couple of their 'extreme' trails left -> I missed it dearly.

when i first put it in i was all gung ho about using it. i pretty much have forgotten about it and only use it when airing up my tires with the york oba now.