Sometimes merchants will turn off 3d secure because of the approval drop with 3ds. This is one of the main reasons why 3dsv2 was introduced to elimate the friction.
Even with 3dsv1 the liability doesn't always shift to the issuing bank. For example, I believe it is Mastercard NA(Might be Visa NA) that doesn't allow any 3ds liability shift for high risk merchants.
Source: Worked at payment processor in high risk processing +$1B in volume
1. It tries to gather more data points about the customer environment (i. e. browser and screen details). I think the goal is to provide more signals that the bank can use to decide low/high risk transactions. This likely feeds into...
2. Some transactions can be passed through in a "frictionless" manner. Instead of getting the "please log into your bank this is not phishing trust us" interstitial, it requires no interaction.
If most of the time, customers are sitting int eh 'frictionless" universe, then they won't hit too many situations that encourage cart abandonment.
Even with 3dsv1 the liability doesn't always shift to the issuing bank. For example, I believe it is Mastercard NA(Might be Visa NA) that doesn't allow any 3ds liability shift for high risk merchants.
Source: Worked at payment processor in high risk processing +$1B in volume