A couple of years ago a Wikimedia Foundation fundraising report explained why that "Don't scroll away" phrase was added:
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“Don’t Scroll Away”
A simple, yet effective phrase that we were surprised to see resonate with readers worldwide was simply asking readers not to “scroll away” from or “scroll past” the fundraising message in the banner. We believe that addressing the context in which people donate helps improve the donation rate.
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Quoted from this report: https://meta.wikimedia.org/wiki/Fundraising/2019-20_Report