Wait until you get to legato techniques and enter the debates of what notes should be picked or be played legato :).

Joking aside...what alternate picking did for me was allow my playing to sound more rhythmic and more fluid. Playing with all downstrokes can give you playing a more choppy or stacatto sound. That may very well be the sound you are going for at times, but as others said, it's good to have options!!

Jeff pointed out about how the picking direction impacts the timber of the note. This is where it can make you playing more rhythmic. Notes played with a downstroke tend to get more emphasis. I imagine it like I'm hitting a drum harder to emphasize a beat...and I more naturally do that on downstrokes. The up down of the alternate picking helps me keep the feel of the rhythm, like I'm strumming chords.

I never sat down and said "OK, I'm going to learn how to alternate pick". Way back I tried learning some licks and the only way I could do it was by alternate picking, so I just naturally started doing that. So yeah, don't worry about any dogma, just do what feels right to you. Try some alternatives if you feel the need and go for it.