While the highest purpose of a chemistry lab is not about pouring chemicals, the act of handling and pouring chemicals can be a critically important skill, depending on the nature of the chemicals. In elementary school mixing vinegar and baking soda would not really matter, as there can be little harm. And while there are some careers in chemistry where you never touch chemicals, a lab does have safe handling of the chemicals as a skill... how to use a pipette, how to pour without splashing, etc.