Why is it that a residential address isn't required during the donation process, even though I would like to send a receipt or thank-you letter by mail?

In our donation process, mandatory fields include full name, email address, and phone number. We intentionally don't ask for a residential address based on our research, which reveals that more questions lead to higher abandonment rates. Our strategy is to minimize inquiries to enhance donor satisfaction and maintain high conversion rates, with a significant percentage of visitors completing the donation process.