Earlier quoted context omitted.
Its rather expensive (and time consuming) to produce reports like this. They are doing it to generate leads.
If there is a cost associated with producing content and that cost can’t be recouped by the presentation of that content (speaker fees at conferences, advertisements, sponsorships, etc) then the content should be sold for a fair market rate. That’s basically the entire point of GDPR. Stop making people trade personal information for “free” content.
You're free to not share your email if you don't want to read the report. The rest of us can make our own decision.