I think it is fantastic you like two very large tv/monitors. For my purposes, I have found two 19 inch monitors is ideal. Almost like two large book pages. Anything bigger and my eyes spend too much time searching.
The point is - Windows should be customizable for a variety of uses and users. That's what makes it superior to any Mac OS. Windows can handle an amazing number of hardware combinations. Fair - windows developers can't predict every use - but this something that a lot of people complain about.
And here is how MSFT replies to this concern:
The key thing to recognize is that the problem is not necessarily that the taskbar doesn’t span, but that more room is required to show more information about windows. So, it stands to reason that we should come up with the best solution to this problem, independent of how many displays the customer has. We thought it would be good to just offer a brief discussion on the specifics of solving this design problem as it is one we have spent considerable time on. One of the approaches in general we are working to do more of, is to change things when we know it will be a substantial improvement and not also introduce complexities that outweigh the benefits we are trying to achieve.
Sounds like a politicians response.
But, really, I wouldn't expect them to spend lots of dollars on improving something that less than 1% of people use. In fact, I doubt that even 0.01% of people use multimon. And of those people, how many want a taskbar that stretchs? Half of them? So, can you really blame MS for not putting valuable resources into this?