User blog comment:Fullmetal Renkinjutsushi/Did Satou waste some of his skill points ?/@comment-32598341-20200207122223/@comment-26680718-20200207142207

You are right. He did have a lot of points. But thing is, new skills are always appearing. Resistances too. You never know when you are going to face a new enemy who has skills on par with your best ones. So that's 10 points for becoming resistant and 10 more for mastering a super awesome skill.

It would be ridiculous if he can't master a skill that grants control over an aspect of nature because he invested it in learning to ride horses.