[dredmorbius]

Cost.

Email is pennies per thousands.

Phone calls are cheap especially for nonconnected or robocalls (which would cost for a postal contact).

Postal mail costs $0.50 US in postage alone. The full-up cost of a mail campaign is often several dollars per mailed item, though in bulk, and with bulk rate, I believe it's closer to $0.40 (postage plus a few cents for paper and envelope).

That would cover many thousands of email contacts, possibly nearly as many phone/VOIP attempts.

And the systems required to successfully and accurately generate a postal response on request are also high.

Low-cost systems are high-fraud systems.