its slow(at 4k) its a generation out of date and the 1080 is a better alt ?
Assuming that you aren't trolling and assuming you haven't read the discussions here. I'll try my best to give you summary of what was discussed
Being Microsoft's first attempt. It's a good guess that this has been under development for well over a year(or longer). And it's highly probable that the design decision was made before the 1080 was an option. If you have any real life experience in the corporate world or just common sense for that matter. You would know that they don't just "toss" in a new graphics card when the machine is already on the assembly line.
Now, with that said. You can probably tell that the Surface Studio was never meant to be a gaming machine from its form factors. For the majority of the content creation needs the 980m is in fact overkill. But I'd like to see TB-3 port include next time so I can run a eGPU through it.
Feel free to enlighten me on a example of a equally specced machine with the same level of design and material involved and we can discuss further. (The screen on the Studio itself is probably worth 1500-2000$)