Why can I not place a tile that scores more than 10 points in Kodama: Tree Spirits
My guess it is to keep the tree growing in many directions and not just along a single path. Since scoring is based on how many icons from the card you played are on other cards in a path to the bottom it would make the most sense to never branch off and victory comes down to who gets the best card draws. With this rule in place there is more strategy to where a card is placed not only to maximize your points but to minimize other players points.
Rules

After placing a branch card, look at the icons on that card. You score 1 point for each instance of those icons in that contiguous line of cards. You do not score points for other instances of that icon if they are not part of this contiguous line of cards.


You only score points based on the icons on the branch card you added this turn. Those icons must be part of a contiguous line of cards with the card you just added. Any other icons elsewhere on the tree do not score points.


The contiguous line of cards extends from the card you just added, continuing down toward the trunk or until the shared icons do not appear on a card.