Nope, I disagree with you.
A business does keep some capital back as a saving for a rainy day... The problem with Bitcoin/Merchants are that they use Bitcoin as a vehicle to get more money, and then they hoard none of it, and they just convert back to fiat. They will then pay their overheads and deposit the rest in a savings account at a bank.
Does that capital they keep in the bank lose 30% of it's value over a few days? Companies cannot afford to operate by saving funds in a currency that can rapidly deplete in such a fashion and that's the reason companies use payment processors.