They're not open at night. They take egregious fees, often up to 20% on the exchange rate. You can't send more than $2,500 online. And who wants to stand in line, fill out paperwork, or walk around with large sums of cash? If that exploitative company is the best example you've got, I rest my case.
They usually have both a flat-rate transition fee, and some spread they take on top of whatever open market exchange rate would otherwise be.
For small transactions, you can have things like a $29 fee, for a $500 transaction, where the spread is also taking a 1% cut. You also can find $2.99 transactions. It depends on the source of funds and destination. Also if you are doing something like using a credit card as the source of funds, you might get cash-advance fees (and much worse interest rates).
