When you talk to people, they're more likely to support their assertions by citing sources with precision than when they write? Really? When I talk to people, I

When you talk to people, they're more likely to support their assertions by citing sources with precision than when they write? Really? When I talk to people, I get a lot of "I read somewhere that X is true" and "I heard from someone that Y is true". And when I request sources, they say they'll get back to me, but they rarely do.