Just for the record, many people are not complaining about a tube of Colgate Extra Whitening Gel available at any drugstore in many, many sizes. Others, and me, are complaining about things that are more difficult to get such as OTC sensitive teeth toothpaste or toothpaste that does not contain the irritant sodium laurel sulfate (found in most soap).
These are generally available from a dentist, and can often be found in drugstores, but often in sizes heavier than 3.4 oz. This is because (and I AM an expert at this) they are specialty items and to keep the cost of production low enough, they are produced in larger quantities. Also, because the consumer is inelastic, read they NEED this product, they are often quite a bit more expensive than generic toothpaste, so it sucks to have to toss it out and buy a new one at the other end.
TSA should not be in the business of telling me not to do what my dentist and dermatologist told me to do.