The test is easy, but has a relatively high false positive rate. It also may use up lab resources that could be put to other uses.
The other wrinkle (and possibly the most important one) is that we don’t want to create a system where antivaxxers have an incentive to deliberately infect themselves and/or others.
I was under the impressing that the Roche test was an outlier, and that most other tests do not match that. Most other tests have issues with cross reactivity with common cold antibodies.
