Because it doesn’t work. You’d need a foot ball field of area, and a 3 story building, to life a small yacht like space.
The wind forces on the surface would be extreme, and you’d need a lot of power to even stay somewhere stationary instead of flying away. All of this would add weight, increasing the volume of helium needed, increasing the wind exposed surface area, making the problem worse.
You’d need a huge industrial hall to store it safely on the ground, and you can’t tie it with a rope anywhere.
The helium required to fill the balloon would make the operating costs of this thing absurd, cause it’s a lot of helium, that leaks all the time and have to be replenished, and helium is super expensive (and necessary for pricy things like cooling superconducting magnets applications, which have infinite budget).
Any 3rd year University student with basic knowledge of fluid mechanics, thermodynamics, and mechanic, can draft in a napkin why we already know that this can’t work.
I’ve sat in meetings where the VCs contracted me and others to do DD on these types of companies, where every contractor told them that this can’t physically work, and the VCs with too much money take that knowledge and translate it to “very high risk investment”. These companies got 100 million dollars and burnt through them, without nothing to show, but for the VC was more important to not have that money parked somewhere and be able to tell investors that they have “mobility companies” in their portfolio, which I think is borderline misleading / scamming because everyone knew that these companies “concepts” couldn’t physically move a thing, cause that was a physical impossibility with the tech that they wanted to use.