You can make the case that reducing tire resistance, which can be done at relatively low cost IS actually something that is more likely to be noticed by an "unfit" rider than a lot of more expensive upgrades. Unlike drag, tire resistance doesn't increase with speed, so you're actually feeling it as you accelerate from zero up through your top speed. Reduction in drag is probably not something you're going to actually feel until you hit some moderately high speed. Also, assuming that unfit riders tend to be significantly heavier than "fit" riders, they're also less likely to feel as much of a benefit in reducing the weight of the bicycle as that reduction is going to be a smaller percentage of the gross vehicle weight (rider+bike) than if they had lighter bodies.