That's highly dependent on the type of development work. I'm a kernel developer and I need regular access to privileged components of the system for a wide variety of reasons. It could be argued that all standard *nix/windows/mac systems need a better security model to better isolate specific tasks, but for much of what I need to do (e.g., create, modify file systems/boot loaders/kernels, ptrace processes, etc...), if I'm allowed to do it at all, I can get anywhere else anyway, so I may as well just have full admin and save everyone some headaches.

And I'd argue this isn't only true for kernel development. In some cases, sure, but certainly not enough to make such a blanket statement.

You shouldn't be doing your kernel development testing on the same machine as you do your office tasks.

Though I will agree there are exceptions, you are not one