It has little or nothing to do with risk. Professional athletes make extraordinary sums of money, and some percentage of that is given to the government via taxes. Amateur sports generates little to no money; therefore, the government doesn't allow it.

See also: here in California, churches/synagogues/temples are closed, while liquor stores and marijuana shops are considered "essential businesses". Film crews are allowed to operate in mass numbers outdoors, but not distanced patio dining.

It seems pretty clear it's all about the $$$.