What a postal address tells you that an email address cannot

An email address tells you a domain. A postal address tells you a business.

Territory

If you sell regionally, the address is the only field that reliably tells you whether a prospect is worth contacting at all. A .com tells you nothing about where the company trades.

Legitimacy

A real street address is a weak but useful signal that there is a real operation behind the website. A business with no address anywhere on its site is worth a second look before you spend time on it.

Route planning

For anyone doing field sales, the address turns a list into a route. That is a completely different use of the same data.

Why it is often missing

Most small business sites publish an address as plain footer text and never mark it up in a structured format. Tools that only read structured data find one in about one company in twenty. Reading the visible text as well, carefully, raises that several times over — but it has to be done conservatively, because a wrong address is worse than none.