The answer is liquidity. Think about it in terms of actual liquids - honey is really sticky and slow to get in and out of, but water is smooth and fast. Now just replace it with assets, and it kind of makes sense. Cash is liquid because you can quickly convert it into any kind of asset (so it’s water), but converting other assets into a medium of exchange is usually slow and it often carries other costs, which are referred to as friction costs (so this refers to the honey).
