At roughly 240 km, Rishikesh is one of the few genuinely feasible weekend trips from Delhi - about 5-6 hours by road, or a train to Haridwar followed by a short taxi ride. That short distance is exactly why it's become the default "quick adventure fix" for Delhi-NCR residents rather than a destination people plan months ahead for.
Because the trip is short, most Delhi-origin packages compress everything into 2 days/1 night: arrival and rafting on day one, a riverside camp overnight, and a short second-day activity (bungee, cliff jumping, or a temple visit) before heading back. Longer 3-4 day versions usually add a yoga or wellness component instead of more rafting.