I'll try to explain my reasoning, then.
If Netflix and other very profitable companies are, as I'm told, contributing in both code and money to FreeBSD, and if I'm also being asked to donate, then the contributions from said corporations are obviously not enough to cover the costs of FreeBSD development.
Since I pay for Netflix, why should I double-pay by donating to FreeBSD? Seems to me that Netflix should be digging a little deeper into their pockets.
I don't understand your point re: Windows. If companies are paying for Windows, then Microsoft is receiving a payment which they have presumably set at a level they deem sufficient to support continuing development of Windows and other projects. I see no parallel to my point about FreeBSD other than the fact that both are operating systems.