What is the reason themes are limited to 15 custom settings?

I find the custom settings in the config json to be very useful, and I got interested to know why there is a 15 custom settings limit in newer versions of ghost (I am pretty sure I did not get warnings previous to version 5.2x for having multiple settings).

Is it a performance issue, or a away to avoid conflicts in the config file, or just a way to make developers come up with smarter ideas?

I use to have over 30 custom settings with no problems, but I had to hard code a lot of them in my theme because I started to get error messages when making new updates.

(keep up the great work, Ghost team!)