Because you realistically don't need any physical hardware to make digital music. A laptop and some software is everything you really need. Perhaps a microphone for vocals and a cheap keyboard controller for input.

Everything about Teenage Engineering and related synths are toys. You can make real music with their toys but they don't do anything you couldn't do on your laptop.

The stuff TE makes are incredibly high build quality and beautiful toys though. I used to have an OP-1 for a while before I sold it. One of the coolest coffee table toys I've ever touched.