I think that the smaller squares are done for 2 reasons, one is for ease of sewing. As your block gets bigger, you will have more difficulty keeping it flat because of all the small pieces and the grain going every which way. The second is that a solid sashing gives your eyes a place to rest and makes the quilt a bit more cohesive, but it's just a design choice.
If you would like to eliminate the sashing, that would be great, but i would recommend to keep the blocks. They don't all have to be the same size, you can make them multiples of 4" for instance, or all rectangles etc, or all 24"...