[evilduck]

Because I weigh the potential of being marketed to by email as being a negative value greater than the potential positive value of the information provided in exchange. 'Free (with the potential to spam you later)' is a world apart from 'Free, gratis, enjoy'.

[FooBarWidget]

The author loses much more than you. You can always unsubscribe, or — if you don't trust unsubscribe — filter away his emails. From the beginning you were always in full control. Giving your email grants the author no power over you whatsoever.

[Terretta]

Nope, they can sell the list (or have it hacked), and then YOU are screwed.

[FooBarWidget]

They sell the list and then you can still filter out unwanted emails.

[marktangotango]

You are being down voted because this is a shallow view. The expression of interest tied to an identity has value. For proof see Google, Meta, Amazon, and Facebook earnings.

[christophilus]

Wildcard emails for the win.