Front axel engagement

[KyFarm]

I have an '04 F250 4wd. It has an electric engagement switch to go into 4hi or lo. If I turn it on I get power to one side of the front axel. If I get out and lock the hubs then I have power to both wheels. That system seems to be what all modern 4wd trucks have whether it is electrically actuated or using a manual shifter.

On these old truck you get no power to either front wheel until you lock the hubs (and switch to 4lo or 4hi) and then you are in a lock situation and it is my understanding that is best for only going in a straight line.

What is the different system that enables modern trucks to send power to at least one front wheel without getting out of the truck and why are they not being commonly adapted to these sweet old trucks that we all love to have?

Thanks for any help on this question......