What SI unit is used to describe liquid volume?
Any volume is rendered in the same unuts in SI: cubic meters, the cube of the length unit.
Yes, that is cumbersome for laboratory work, as you commonly deal with liquid volumes in cubic decimeters (liters) or cubic centimeters (milliliters). But in industrial settings, especially with gases, cubic meters is a very convenient volume unit.
No one ststem of units, not even SI, is optimum for every application. In fact, one reason to use scientific notation is to deal with the large or small numbers that may arise when we render our process variables (like mass or volume) in units that don't fit neatly with the quantities we are using.