When you TIG you have to add filler metal with another rod, often a tricky figure-8 stitch motion with the gun in one hand, and a dip-dip with the rod in the other.
When you MIG, the added filler metal acts as its own electrode. No fancy motion, just pull the trigger and move at a very steady rate. In reality, the arc often strikes and breaks repeatedly and very fast, looking continuous, and you can tell a lot just by the sound, whether it's crackling or just a continuous burn. So even without remote current control, you get some current control via the wire feedrate. What's nice about MIG is that it's pretty consistently repeatable; once it's set up right you can just go and go. The downside is that you can't alter things mid-weld easily. There's less technique needed, but less technique allowed?
And if you want to weld your frame with MIG or TIG, you'd better have a welder the size of a small car to do continuous welding on thick aluminum. OK I exaggerate, but the guy next door has an enormous TIG in his garage for working with stainless, a true artisan, but he can't weld thick aluminum with it because his house supply from the power line on the pole won't supply enough current at that higher voltage, just not enough amps in the residential supply line. Aluminum not only sinks heat, it conducts electricty really well. But yes, ultimately a hell of a lot of the power ends up as heat spread all throughout the part.
BTW sometimes you see TIG adapaters for stick welders. Gas solenoid valve, high-freq converter, etc... I saw one in Trading Times built specifically for my big old Miller stick welder, but it was sold before I called.
