> I’m pretty sure that in most countries, a store can’t just sell another company’s products without entering an agreement with them.

Of course you can. What makes you think you can't?

The fact that your company’s product end up being represented by the store and its actions. Mistreating employees and customers, discrimination, bad customer service/return policy, terrible product placement, etc. There are so many ways a store can hurt your company’s reputation by association.

But I mean there just isn't any law like you think there should be.

People are free to resell any goods they own (exceptions for things like controlled substances, other things with regulations etc.)

Look up 'grey market'. Lots of companies try to do what you suggest, but in the US there are very few laws that support such a business model.

I don’t know what countries are like that, but that’s certainly not the case in the United States.

It is, even amazon bans resellers sometimes.