Governments have a difficult time giving up powers once they have them. So even if it is morally right to give the government extra privacy infringing powers to save lives today, it is not morally right to compromise the privacy that generations of citizens who come after us will need in order to exercise their right to self governance later.
The best of all worlds is where the government says, "look, our responsibility is to look out for your health AND your other fundamental rights, and so we need this, but we want it to respect your privacy too". Which is what governments who choose DP-3T are saying.
The best of all worlds is where the government says, "look, our responsibility is to look out for your health AND your other fundamental rights, and so we need this, but we want it to respect your privacy too". Which is what governments who choose DP-3T are saying.