It depends, I have shopped at places where they will discount up to 15% by paying cash.

sellers are not going to lower prices based on payment method

Mullvad actually does this for their VPN service, which I think is great. For a VPN company that doesn't want to store identifiers about you, taking crypto makes sense because that also doesn't necessarily have identifiers about you attached that they could read or be required to store, unlike a card that requires your name, address, and card number.

Other than that though, no larger companies are going to do anything of the sort, let alone be likely to even implement it as a payment method to begin with. Tons of additional technical complexity for little to no benefit.

Sadly, this is probably true. Unless they're trying to steer customers away from more troublesome payment providers.

That's actually one of the matured parts of the crypto ecosystem that has existed for years already, as it was one of the most immediate needs. Last I checked Stripe and Bitpay were the most popular options for vendors.