Most of the cassette resurgence has been with avant-garde/underground music and noise. Much of this kind of music was distributed on tape before CD-Rs and burners became widely available. They could be made at home or outsourced in small batches; vinyl is always outsourced and minimal quantities are usually much higher. For many of these artists, vinyl is an unaffordable substitute for the now maligned CD. Downloads are an obvious option but there is still a desire for tangible objects, especially ones that have often have a handmade quality to them. The psychological connection between the artist and the listener is often stronger when it is known that the object literally came from the artist's hand.
As for the agenda of hipsters, who the fuck cares....