This is why most modern music is played with a click track.
Contemporary music began using a click track because it makes techniques like sequencing, non-linear editing in a DAW, and tempo-synced effects far easier to incorporate. Click tracks and rock-solid tempo are also an aesthetic choice.
It's far more difficult to sync these techniques to a wavering tempo, so the trend has been for bands and records to conform to the click as the central authority for the pulse in order to unlock the benefits of the above-mentioned techniques.
The author's product allows users to slave the click track to the drummer's playing (which may now waver). This opens the door to real-time tempo-following by the click. The band can now push/pull the tempo AND use all of cool synchronized techniques in real time.