This picture is a nice example of why splines are useful. In my favorite 3D graphics software Autodesk Maya, I often use the CV Curve or Bezier Curve tool to create half a 2D cut of cups, vases, or wine glasses. All you have to do is revolve the spline around the y axis 360 degrees and you've created a NURBS cup/vase/glass in 10 seconds. It would have taken at least 10 minutes to model the same thing via extrusion and smoothing with regular polygons. Also, you can easily convert the NURBS model to polygons with a click of a button, so Spline generations of these cylindrical objects save lots of time. As a bonus, you can change the shape of the model afterwards easily by just adjusting the original spline, so you would be dumb not to use a spline to model these.
How would you model a square cup (bottom right corner) and the handle (bottom left corner)?
Lighting glass for photographs is always a fun challenge. There's a good how-to video from the youtube channel slanted lens (his name is jp morgan but no relation to the bank lol) that shows how to light glass. https://www.youtube.com/watch?v=M9NlA7yzFrw. Tl;DW glass likes to be backlit, and there are different ways to shape and remove light to highlight the shape and depth of the glass. I think it's fascinating to watch the way photographers and videographers shape light for glass in product photography and can really provide some physical intuition for how we can model light in graphics.
@alexkassil: You'd probably not use splines and rotations to model a square cup. Instead, you could start with a square block, then extrude the center inwards.