Really? I don’t ever recall being asked that.
According to the FEC, all donations that aggregate over 200 should report employer. So, if you make four 50 dollar donations, they have to report employer... ergo they ask for it for almost all contributions. If you go to the Save America Pac and donate, they do ask for employer but put an asterisk on it explaining the 200 dollar combined requirement. If you keep it under 200 total, it does look like you can avoid putting in your employer.