I'm not really sure, but my guess is because they have a variable composition, as apposed to compound or elements which have fixed compositions.
Hope I helped! :D
This is a mixture not a compound with a chemical formula.
Dishsoap is a mixture and so does not have a chemical formula.
Obsidian is volcanic glass, a mixture and as such has no chemical formula.
Toothpaste is a mixture, not a compound and so there cannot be a chemical formula.
There is no chemical formula for a mixture. Water has a chemical formula, soft drink, milk, yogurt, wood does not. Rust has a chemical formula, however, yogurt, ice cream, pancakes have a recipe - no chemical formula.It is a mixture, not a compound
A crouton is a mixture of a ton of things, and therefore does not have a chemical formula.
Cheetos is a food, a mixture of products and chemical compounds - no chemical formula of cheetos.
A vaccine is not a chemical compound it is a mixture.
There is no chemical formula for the product soybean oil. This is because soybean oil is not a chemical but a mixture.
H2SO4W3FE5O6SO3 + nitrous oxide = Arizona ice tea
Oil is a mixture.
There is no chemical formula for chocolate, merely chemical componets of the ingredients. This is because chocolate is a mixture of these ingredients, and not a compound.