Why is soaking water usually discarded when making plant milk? Most recipes that I see for soy and nut milks ask you to soak the seeds and discard the soaking water.

The only plant milk recipe I've used that keeps the soaking water (Scratch Soy Milk by Andrea Nguyen) turns out just fine.

I've also experimented with using the soaking water in almond milk, and this too is fine.

So why should I discard the soaking water? Is it just a matter of taste, or is there more to it?
Generally, we soak grains and pulses then throw away the soaking water. If we didn’t it would likely turn sour in a few days. Also soaking helps remove some of the phytic acid, therefore unlocking more nutrients. I suspect the phytic acid will be in the soaking water which we flush away. Phytic acid prevents absorption of a number of minerals.