For touring, a modern titanium framed, disc brake, belt-driven 252-speed touring bike with tubeless tires just can't be beaten.
Okay, we got that out of the way, so onward down the rabbit hole. Sturmey-Archer three-speed hubs were born out of an experience where one Mr. Frank Bowden hurt his knees on a bike tour in France - in 1887!
Lotsa folks have toured using three-speed hubs in the last 116 years. They've day toured, overnighted, crossed the USA and ridden around the world.
Frank Berto theorized that historically the French (Huret) & Italians (Campagnolo) developed the derailleur drivetrain for their long mountain passes and sunny climes, while the British (Sturmey-Archer), low countries and Northern Germany (Fichtel&Sachs) went with the hub gear for their flatter terrain and damp weather (their steep hills are short enough to be walked).
The Sturmey Archer 3-speed hub produced today is basically the 1936 AW (nicknamed the
Always
Works) with a few small improvements. It has stood the test of time and is easily the most complicated bit of cycling kit with that length of production. It's built today on modern, computer-controlled machine tools.
The three-speed
Internal
Gear
Hub is a serious mechanical device, used in demanding service on millions of bike-share rent-a-bikes worldwide. In the single year of 1939, Tommy Godwin rode a total of 75065 miles using a Sturmey Archer 4 speed hub gear, a record that may or may not still stand depending on various caveats. A three-speed hub is also a jolly bit of cycling fun. Every May the two-day Lake Pepin 3-Speed Tour is held in Red Wing Minnesota just for three-speed bikes. There are hundreds of entertaining and inspiring pictures of past Lake Pepins on the web.
https://3speedtour.com/Currently, the Society of Three Speeds is hosting 'Adventure April'. This challenge involves riding a 3-speed bike for distance, climbs, a bit of gravel biking and an overnight tour. I signed up and I'll be riding my Dahon Curl i3 on a two-day tour over Easter weekend.
https://societyofthreespeeds.wordpress.com/3-spd-apr/Aspirational current production three-speed bikes include the Pashley Guv'nor, the Shinola Bixby and Brompton S3L-X.