Salespeople are supposed to give you some sort of material with their contact information, including website. It’s what is expected of them and is a standard sales practice. Doing so is a proven technique to increase repeat business and improve customer satisfaction. Even when the sale isn’t closed, giving the customer a business card increases the chance that they will return to purchase.
I know, we all think we just toss the cards and no amount of marketing works on us. We’re wrong.
When shops require you to get a business card, it’s because the employee is supposed to proactively offer one. When you can’t get a business card, simply explain why not. Usually, they want to find out if the employee, who should have business cards, actually has them.