Shimano did this out of necessity. Before Tiagra 4700, upgrading to 11 speed necessitated pretty much a whole new groupset, but since the introduction of 4700, someone wanting to upgrade to 11, and who knows 12 speeds need only change shifters, cassette, and chain, much cheaper. 11 speed required a whole new cable pull ratio, the previous generation 10 speed setup couldn't be stretched to 11 speed