It's a toy that can go up 50 feet or less. You can't scale it too much. To get to space you need like 100km (x6000) and then a lot of speed sideways to get to orbit.
This model works with a drop of fuel that evaporates and mix with the air. In a real rocket you most inject the fuel and oxygen from the tanks into the very hot and high pressure burning chamber, so you need pumps.
I think the reason can be the industry incumbents - there just isn't much money to be made with such a simple design, only a nozzle and combined fuel and oxidant tank in PET plastic which can be recycled, no moving parts.
