The dictionary definition of "merge" is: "to become combined, united, swallowed up, or absorbed; lose identity by uniting or blending." Hence, it is the responsibility of the vehicle entering traffic to "lose identity...by blending." After all, the sign that says "MERGE" is on the on-ramp.
You do not "lose identity" when you drive up the ramp slowly, fail to look in your mirrors or turn your head to see that there is oncoming traffic, cause someone to jam on breaks for a panic stop and "expect" the oncoming traffic to make room for you. When you do that, you GAIN identity as the jerk to whom my DD would say, "It's called MERGE; look it up!"