KnowBe4 Security Tips - WiFi? Why Not? VPN is your friend
Using free public WiFi at a coffee shop or airport hot spot is great for convenience, but bad for security.
Most free access points do not make use of encryption. This is done for convenience and ease of access. If every person had to ask the barista or gate attendant for the WiFi key, it would get unruly, and no actual work would get done.
Keep in mind that you are sharing those wireless airwaves with anyone that is within range of your wireless communications.