man people are lazy - it's literally right there in the intro: "Flow-based deep generative models conquer this hard problem with the help of normalizing flows,

man people are lazy - it's literally right there in the intro: "Flow-based deep generative models conquer this hard problem with the help of normalizing flows, a powerful statistics tool for density estimation. A good estimation of p(x)p(x) makes it possible to efficiently complete many downstream tasks: sample unobserved but realistic new data points (data generation), predict the rareness of future events (density estimation), infer latent variables, fill in incomplete data samples, etc."