The USPS is so convenient and inexpensive that I’ve switched almost entirely to email, online billing, and the occasional fax.
So have I, but there are still the occasional things I have to mail by the USPS. As for expensive, mailing a package is often cheaper with USPS than it is with UPS or FEDEX. There is no reason the USPS has to be so inefficient, Unions are the problem, or at least a large part of the problem.