Of course there are still sculptors around! Like most art sculptures have gotten more abstract tho. Visit any museum of modern Art and you are sure to find some!
Marble and the like are of course incredibly expensive, and for that reason most people stick to more affordable options like wood or ice. Or do additive sculpting with clay/plaster, welding or something like that. If you really want to work with stone you might want to apprentice with a stonemason.
How did I start? Took a pocketknife in my hand and started whittling. The foundations of working in a subtractive manner are largely independent of material.
I mostly agree, but saying nobody ever sculpted in marble is a bit like saying nobody ever painted with oil paint because most of the most well known oil paintings were done according to sketches made with charcoal or pencil.
The finished sculpture is made of marble, and thus it was sculpted in marble. Not at first perhaps, but eventually