It's interest-free for the customer because the interest was already bundled in the good's price.

It's risk-free for the retailers, as the full purchase amount is taken from the customer's credit card limit, but they will only receive the money in installments, unless they opt to receivables financing.

There are retailers that offer discounts if you purchase in one lump sum. Now recently some banks started giving discounts if you pay the installments in advance.

This is common in high interest countries as there is this whole financing industry that revolves around customer credit, and as the interest rates are high enough, there is lots of money to be made.