What counts as “sketchy” wifi?
Public or open wifi, even with a password can be monitored.
2 years ago connecting to open wifi was probably ok for most people, but the playing field has changed. It is cheaper and easier for malicious hackers than ever before, and wifi like coffeeshops and airports is especially vulnerable.
Manipulating unencrypted (http://) websites
Password-free or public wifi can have issues where the person providing the service can monitor and manipulating the websites you are requesting.
Watching address in encrypted (https://) websites
Even when the website you are visiting is encrypted, the website address you are requesting can be seen. This can open you up to spearphishing attacks.