they make money by catching u forgot to pay.
cuz unlike credit card, where u get a statement via email, or sms reminder, atome dont do that.
when shopee pay later just launched, i tried it out. to my surprise, it says due date on 1st Nov for example, & on 1st Nov, it already charge me RM10 late fee.
i was not satisfied & argued that 1st Nov due date means 1st is the last day to pay without penalty. that's how bank repayment works.

also, for just 3 months, they are not really losing much interest compared to the shops they attract to platform.
it also encourage people who cant afford the item to spend more.