I don't use weights because it's more accurate, but because it's just for me easier. I'm alittle ocd about cross-contamination, so I would need different syringes for each ingredient, or else I would have to spend like 10 minuttes inbetween ingredients to clean up the syringe and propperly dry it...
Measuring by syringes is fully accurate enough for me, but I just strive to make it as easy and convenient as possible, hence for me, meassuring by weight is the best...
That the substances is liquid is imho irrelevant; liquids has a weight nonetheless, and of course I see the point that its not really "that natural", but I would rather have the convenience of using a system which could be thought off as an all powerfull dynamic syringe that both never needs to be cleaned and that always has the right volume for the ingredient at hand e.g. from a 1ml syringe to a 100ml in an instant and without cleaning.