It's overly complex for what I do, which is mostly hobby stuff with some occasional custom designs for my work use (academic research lab, mostly custom mounts and brackets for obscure equipment). Also the onerous licensing and price. Admittedly it's been a while since I used it, so maybe the UI is more friendly nowadays but I never really found it to be particularly intuitive.

But the biggest reason is I'm a Linux guy and I want something I can run without rebooting into Windows or a VM. I'm usually extremely wary of complex applications running in a browser, but I have to say OnShape works great and performs well. And being in browser means it runs on Linux no problem, which is a major benefit to me.