For many nurses it is a matter of personal safety.
In modern America, products that might cause death are frowned upon.
Lawyers and the federal government have convinced Americans that every product should be 100% safe. Covid vaccines simply do not meet the now expected American standard of 100% safe.
Perhaps hospitals could offer their now unvaccinated staff testing before vaccination, to get reference levels, and at say post-vaccination day 1, 2, 4, 8, 16 and 32 with complete blood counts to monitor platelet levels and D-dimer and platelet factor 4 testing as medically indicated.