Thank you for the playing the game and taking the time to submit feedback!
The level cap was designed around the content within the game (it is fairly short), so that the average play-through would get you close to the cap but still allow you access to most or all of the skills. I also didn't want anyone to feel like they had to grind to succeed if they hit a difficult fight either (since the final fights were designed to be beat-able by a level 8-9 party), nor did I want people to be disappointed if they continued to grind but never gained access to new abilities past level 10.
Personally I dislike grinding in JRPGs, so I appreciate your perspective. It would not be a big issue to raise the level cap, but I wonder if it would cause frustration for other reasons.