So this is another step for Apple to try to get everyone paying them their software development tax, since "notarization" requires you paying the $100 annual fee.I don't think Apple really cares about the fee. I know that the three platforms are now bundled together under one developer program, but suppose that there are 100,000 Mac developers that publish signed or App Store applications (which is probably an overestimation), the fees will make Apple 10 million. This is less than pocket change to them.
To me it seems that the $100 annual fee is to prevent fraud: (1) using a credit card to tie the developer account to an actual person; (2) make it expensive enough to avoid playing whack-a-mole with malicious account creation.