They do make that argument, and it is a rhetorical trick. A “corporation” is a legalistic endorsement of several types of business structures. Governments do not create corporations, they only acknowledge and protect their interests. In an anarcho-capitalist free-for-all there won’t be a government endorsing corporate business entities but those entities will still exist.

What libertarians want to trick people into believing is that the freedom that business entities would receive from government no longer existing is a benefit to anyone but the wealthiest business owners. Because what the libertarians don’t say is that without government and laws there is no business accountability and the wealthiest business owners can do what they want no matter how much harm they do to others. That is the ambition of libertarians and why they lie about so much to try to achieve it.