Aye, of course using only drops to mix isn’t accurate. However, using drops has a place. For example, I add one drop per 10ml of FA condensed milk to liquids that want a creamy effect. This one drop per 10ml is the perfect amount for me. The drops are always the same size, as it comes from the same bottle. So the amount added to every liquid it goes in to is consistent. I have no idea what the volume or weight of this would be, but whatever amount it is, I’ve found it to be perfect for me. This is the same for things like cardamom and other spice, herb, floral flavours where a small trace is all that’s needed. There is no advantage to trying to weigh this.
Also, the residue left in the cylinders will generally be a fairly consistent amount, so if you use these exclusively for mixing your measurements will generally be consistent, and since I mix purely for my own personal use, there is no real need for accuracy other than to satisfy my own preference. So if some inherent inaccuracy is consistent, it becomes negligible. No? It’s simply a matter of preference really.