Maybe it's an instance of Parkinson's law [1]: if it all fits in GPU memory, just put it all in and plot it. This is much simpler to implement than any out-of-memory technique. It's also easier for the user—`scatter(x, y)` would work effortlessly with, say, 10 million points.

But with 10 billion points, you need to consider more sophisticated approaches.

[1] https://en.wikipedia.org/wiki/Parkinson%27s_law