learning to sweep and learning efficient picking is just as funky as the first time you try to alternate pick, or play a kick drum.
Sweeping has its uses and will surely speed up your playing... But I don't think it's something that has a use 100% of the time... I also don't think alternate picking has it's uses 100% of the time either.
There are many times where the only way for me to attack a string is through constant down strokes, with the occasional up stroke.. Even if it's on the same string. You could be playing straight 8th notes for 1 bar and then 1 bar of 8th note triplets then back to straight 8th notes. Downstrokes on the straight 8th notes and alternate on the triplets. That's just an example.
But with more complex picking patterns interweaving downstrokes, alternate, and sweeping is more economical than any one style.
It's all relative. Learn the style so that you don't have to think about it. But you gotta get to the point where you go for the most efficient way of picking without thinking whether its downstrokes, alternate, or sweeping.