The quick answer is "to support education." The complete answer is more complex. We believe that encouraging students to learn deductive reasoning is one the more pressing problems in the education system today. We also believe that one of the most important reasons why it is often not taught effectively is that there are simply not enough good educational materials available for teachers to use. We decided to make one type of resource that we believe can be an effective tool for helping students learn and practice logic, freely available for teachers to use with their classes and to financially support this effort by selling the same books to the general public. The "Daily Puzzle Page" provides the most visible free educational resource for teaching logic using Group Puzzles. Another resource derives from granting teachers in grades K-12 permission to copy the puzzles from Group Puzzle books for use in their classrooms, both to actively teach their students logic and to allow their students to practice logic and deductive reasoning on a regular basis.
So why are most of daily puzzles simpler and smaller than the traditional 9x9 Sudoku puzzles? One reason is that it is not clear at this point whether there is a market for books with the easier puzzles outside of K-12 education. Since, to our knowledge, no one has tried publishing puzzles smaller than 6x6, or using any of the smaller puzzles for education purposes, it seems best to publish them only on the web for now to allow teachers to experiment with them. For this reason, the daily puzzle page provides several puzzles of each of the sizes smaller than a traditional 9x9 Sudoku puzzle each day. In addition, we want to provide materials for the youngest possible students, but exactly how young is too young is not clear. We believe that some of the youngest children may be able to be taught their alphabet and numbers using 3x3 and 4x4 puzzles by explaining to them that they should only have one of them in each row or column, etc. In this way we hope that some students can learn the ABC's of logic, so to speak, at nearly the same time that they are still practicing their alphabet, and that this will serve them well through out their education. For this reason, the 3x3 and 4x4 daily puzzles cycle through a set of puzzles defined with different sets of letters and digits that taken together span the entire alphabet. Thus one day a student may work a 3x3 with the letters A, B, and C, and another day with the digits 7, 8, and 9. Each week the cycle repeats.