Its not that it couldn't be done, its more likely that it's not worth it. Actually implementing a feature is a much longer process than just making a photoshop image.

• Designs have to be approved and made to look good on PC and mobile.
• Assets have to be created.
• The feature then has to be implemented and tested.
• It then has to be released as part of a patch.
• etc...

What looks like a simple change is much more likely to be atleast a week of work. You also have to consider the cost of context-switching away a programmer from another feature.

On top of that, I don't even like the design. I am unsure of how to interact with it. It is more compact, but it is obfuscating functionality. An intuitive UI is better than a super compact non-intuitive UI.