Fax technology was used throughout the 20th century to transmit newspaper photos overseas. There were several issues that prevented its migration to popular use until the mid 1980s (not the 1970s as Ingmar said -- in 1983 virtually no company used faxes and by 1988 virtually everyone did.) Improvements in computer chip technology and printer speed/cleanliness allowed faxes to go mainstream.
One other factor was necessity. Bear in mind that if the person you need to fax doesn't have one, it doesn't do any good for you to have one. They started coming into wide use when a lot of Japanese companies were doing biz in the US -- cross communication was difficult because of the time difference, but faxes solved that. Then their vendors got faxes to communicate with the customer, and from there it caught on very quickly.
Yes, the first patent for facsimile transmission was awarded by the USPO in the '50s... but it was the 1850s!. It was for use over telegraph wires. It was two synchronized pendulum-like devices that passed over the source document and deposited the message on the target. It was impractical - no way to synchronize remote devices in an era with no standard clocks - in fact, not yet any standard time zones!
The first use of telephonic fax devices I could find was in early 20th century at the Paris Exposition. A London newspaper supposedly scooped competition by transmitting opening day photos of British royalty. I have not found any documentation for the technology used, or explanation for why it did not catch on a half-century or more before contemporary fax machines.