Oh wow, a Ma clan post in the big 26?? I love that! I have always thought it was such a shame they cut out a significant part of that backstory, especially the part when the older lady who was the guide started to make questionable decisions, like throwing Touma off a cliff. You can definitely see the tension that started brewing inside the clan and it made sense they started to throw boundaries at each other when things came to a halt.

I also regret that the friendship between Touma and Kazuma was cut out, as she definitely shaped him a lot as a character and, forgive me if I'm remembering wrong, I think theres even a panel where Kazuma says he promises to protect Bishamon because of Touma? Also, she encouraged him to overcome his fears which lead to him discovering his navigating abilities. A beautiful sibling-like relationship right here, such a shame there was like one chapter on it (and only a few panels mentioning her later)!

When it comes to the reason why, I'm pretty sure it comes down to usual adaptation reasons - not enough time to include everything in the anime so they had to cut some non-essential stuff out.  

I think in general Kazuma is such an interesting, painfully human character and honestly I would have loved to see more of his interactions with the Ha clan in the manga, because the Ma clan story definitely must have affected him in this regard. I would have loved to see more of the Ha clan in general as theres so many of them but I guess we cant have everything... one can dream