Because it's like a cliché example of an engineer with the view that some relatively successful real-world product—that they have no real insight into—is far easier to implement than the people who _are_ familiar with it have. You see this literally all the time, to the extent that it's become a meme, and it's hard to believe anybody would make that argument seriously.

Spotify might have too many engineers on-staff; reducing the service to "moving between 1MB to 20MB files from a CDN to user's devices" is a flatly uncurious approach to understanding what engineering challenges they might face or if that's really the case. It's a service that _adds_ 100k songs a day, for goodness sake.