Can someone explain to me what the point of drushing is?

Now, its a go-to strategy for most high-rated players, and im not a high-rated player myself, so clearly there is something i dont understand here. By drushing you are delaying your feudal time, and militias are kinda rubbish, i mean, they are not really any stronger than villagers with loom. You are not going to be able to pick of many villagers with such a weak unit, and if you are unable to do so, you delayed your feudal time, where you could be making man-at arms and/or archers. You know, units that can actually do serious eco-damage.

I guess going militia forces the opponent to loom up, and build a few house-walls and palisades, other than that idk. I guess for aztecs its viable simply because of cheer numbers though.