Let's take reading. I am not an English teacher but please consider this question. Do students get to the end of a unit of work and only at that time get to practice reading? Or do students in schools learn to read by actually reading? One would hope it would be the latter, although one may argue that there are some basic developmental requirements that need to be met for them to read, but again I would imagine that these bases are covered somewhat by teachers reading books that reflect these different developmental levels (like small-sided and modified/conditioned games).
So what is my point you might ask? Well, if I were only to teach letters and words and did not teach how to put them together into a sentence or to 'make sense' when reading a sentence then there would not be much point in doing it? However, if I taught students the links between words and the meaning of these words as they make up a sentence, which the students practice by reading, then one would assume that this would help the students more as they went through the unit more than leaving this process to the end of the unit.
So, why do we in physical education teach all the technical skills first and then haplessly hope that the students will miraculously do all of the skills when in an actual game, especially when this game is left right until the end of the unit? Going back to the reading metaphor, surely if one wants to develop the application of skills into a game then this must be taught for it to be caught? Moreover, the likelihood of skills application - from a holistic (technical and tactical) perspective - is higher if the context in which the skill is being taught aligns to the actual context it is needed, i.e. the game!
This begs the question why so many practitioners persist in teaching game skills in this way? To read (play the game) one must read (play the game) so...let's play the game, or something very close to it!