This was likely done to keep the costs down for the end user. Oh wait...
I used this functionality a few times when I was using my MacBook Pro temporarily as a streaming box to the TV. But, I'm not necessarily bemoaning its departure. However, in principle, Apple has cut back so much of the 'Pro' functionality of its Pro line that it's almost laughable. Why would I
ever buy a new model to replace my 2012 rMBP? I feel like I'd be investing way too much money in a computer that was only marginally more powerful with a fraction of the day-to-day utility (i.e. ports, etc.). A 2.3GHz quad i7, 16GB RAM and 256GB SSD seems to still cost the same in 2016 as it did in 2012. What gives?
I am tempted by the portability of a MacBook, but the performance hit and the lack of ports is simply too great of a sacrifice. And, as someone else said on this thread or another, you might as well get a MacBook over a MacBook Pro at this rate - unless of course you want to spend about $3,000 to max a Pro out.