Pocket sumally and liquids

Pocket sumally doesn't allow liquids to be stored, but their definition is very broad. The website says lotion, cosmetics.

I wonder if sticks for lips, or viscous wax for leather treatment counts.

Any idea why liquids aren't allowed?

I asked their support if I could store gel in a sealed container that has no chance of leaking inside a suitcase and they said no.

It seems minikura also doesn't allow liquids. And they don't take suitcases.