You see a lot different cards from the same company and they have different credit score requirements my initial response is "why?".... Then you see things about underwriting requirements. Is there any information anywhere that explains this? In other words if a score of 680 will get you one of the lenders cards why won't it get you others from the same lender
Because each card has different benefits.
Generally, the lower the approval criteria that is required for that specific card card, the less benefits there are. For lower underwriting criteria cards, rather than to spend money on those benefits, the banks are more focused on cost-cutting than spending simply because the risk of this subset of customers they are dealing with is higher, meaning chances of non-payment and default are higher. You don't throw more money at something that you think you aren't going to make much of a profit out of. This is why cards that have lower approval criteria often have subpar customer service, less benefits, and more restrictions.
It's just a perceived profit vs risk issue most of the time.
Benefits the card offers is the simple answer.