Scrutineers also have the advantage of being understood by anyone with a pulse. "Votes go in here, mutually opposing interests watch them like a hawk until they get to the counting center, then the count is watched by those mutually opposing interests. You can be a scrutineer yourself if you're concerned. The record can also be re-tallied if there's a concern".
Compare to voting machines: "Just trust us. You need to have deep domain knowledge in several fields before you can even start to evaluate our trustworthiness (software, hardware, security, etc)... so just trust us. No, you can't examine the machines."
