I take it you have never tried to use the support system of many of these services? Yeah, you may sometimes get a good rep that will actually help you and refund you. More often times than not you are forced to jump through massive hoops, auto replies, no help, etc. to the point that you have to do a chargeback. Also, chargebacks are not always a guarantee, VISA (or whoever) does their own investigation to make sure you're in the right, so you would only likely go that route when you're confident that the service is in the wrong.
I refund routinely on Steam. The only times it doesn't work is if I've played more than 2 hours which seems fair. I don't see why I would be entitled to making a chargeback after I've played the game for that long. That would be like renting a movie, watch it and then make a chargeback.
> Why would you chargeback in Fortnite instead of just refunding?
It's really cool that Steam has a working refund system but I'm not sure it helps with the explanation of why refunding on Epic is an insurmountable challenge.
Steam will even still give you refunds after 2 hours if you have a reason that convinces the customer service rep (e.g. performance or compatibility issues that you spent 3 hours running the game trying to fix)
I hope you are not trying to suggest that something Steam should be commended for rather than just the bare minimum. If the product being defective only becomes apparent after two hours then the product is still defective.