As a customer are there any downsides to using these BNPL platforms when I'm buying something? I generally never buy anything online that I can't afford to pay for it outright so I have never used them before.
They are designed to let people buy impulsively without annoying restrictions like not having enough money. Who would have though this was either an addressable market or a good idea.
I don't get why they are so popular either, or worth this much. They also don't have any moat - any payment provider can offer to do the same thing they do with less hassle for the customer (PayPal has started doing this for example). There are many direct competitors in addition (eg Zip).
That starts you down a very slippery slope of what other things poor people supposedly can't handle, because of course you know what's best for them.
Pay it outright, if you can. It's usually the best way.