4wd Electronic Shifting, what are locking hubs for?

[ChrisCNC]

I recently purchased my first 'real' pickup, 2003 Ford F250 Lariat SD, FX4 package.

I'm confused about the 4wd setup. It has lockable hubs and the 2wd-4wd-4wdLow selector on the dash.

What are the hubs for? It goes into 4wdLow no matter which way the hubs are turned, and the front driveline always turns, even when 2wd is selected. I have a feeling this is the way it is supposed to be, but wanted someone to explain things to me. The manual is unclear.

If it will shift into 4wd no matter which way the hubs are turned, what does locking and unlocking the hubs actually do? And does Ford actually think having the front driveline turn all the time is a 'good' idea?