Because the kids will really enjoy the ride and so will you!
The weight of the bike is essential, especially for the beginner cyclists. A small child usually weighs below 20 kg and unfortunately majority of the kids bikes for this age weigh around 11 kg and more. That would be the equivalent of an adult weighing around 80 kg riding a bike that weighed around 50kg -not fun! Yet we expect little children to ride and lumber around that kind of weight!
This is why we at Rascal bikes use special hi durable lightweight aluminium 6061 tig welded butted frames and especially made components to save every gram we possibly can sustaining the endurance of the bikes. This is an ongoing process and we keep on upgrading our bikes all the time!