The purpose of classical ether was to explain the propagation of light, since all wave transmission require a medium for those waves to exist in. Fermilab mentions it on the ether page I linked:
https://www.fnal.gov/pub/science/inquiring/questions/ether.html"Understanding the properties of the vacuum is the basics for physics topics like superconductivity, the origin of mass, creation of antimatter, and many more. Past, present and future research has been and will be devoted to understand more about the vacuum and its implications to matter, space and time.
The properties of the vacuum are not immediately apparent in our daily life. They, however, become important when studying the microcosm, also called the quantum world.
Physicists have developed quantum theories that can explain many interactions of matter and antimatter, including the creation and
exchange of light."
Another quote, from
Essential Quantum Optics:
https://books.google.com/books?id=Re6Ph5rk2hkC&pg=PA189&lpg=PA189"At the beginning of the twentieth century, Albert Einstein replaced the aether theory by relativity, but a twenty-first century aether is still puzzling physicists today. This modern aether is the quantum vacuum. The aether was thought to be an all-penetrating mysterious substance that carries light through space like air carries sound. Take away all light, and the aether would still be there, defining a universal frame of reference. Now, according to quantum field theory, the state of absolute darkness, the vacuum state, is still a physical state filling space throughout, similar to the aether. There is an important difference though: one does not notice motion at uniform speed relative to the quantum vacuum, but, as we describe in this chapter, during acceleration the vacuum glows, although slightly, causing friction. Furthermore, as Stephen Hawking predicted in 1974 (Hawking, 1974), the quantum vacuum should also cause black holes to evaporate, because at the event horizon particles are created from nothing, at the expense of the black hole's mass."