Easy. If you ban the government to buy that data, but evil corp is allowed to buy it, you now created a business model where evil corp is paid by your government for some compiled version of said data as a service with hefty additional fees on top.

And if you think that is unrealistic you may need to do some research into who pays the bills of Palantir et al.

So if the goal of the ban is to prevent government overreach, you need to ban collection for everybody, except maybe well documenter scientific applications and specific private areas.