I'll just chime in, I think in lower skill brackets where carries get less than half the possible CS even in a purely safe lane. That if you're playing support, that you should not necessarily be trying to last hit every mob, but a few here and there to buy more wards, is good practice. If you never try to CS you'll have trouble when you have to. Also go hard at denies, its like last hitting practice for when you actually play in a more farming prominent role. Stacking and pulling is great practice for map awareness and remembering timings, like rune spawns, stack timings/spawn box shapes. You slowly accumulate the knowledge to improve. Once you get to the point where your carries are >50% last hits in lane then I'd say back off except to fly the courier, or buy a set of sentries rapidly to deward or harass etc but if you make a comment to the carry they usually don't complain.