Because it is the proper solution. It makes the rest of the code simpler if you can just use the right tool.
As I mentioned, C-style arrays cannot be initialized in member initializer lists, which seems to be the goal here, so you are forced to pass it by reference or by pointer and/or copy the contents manually.
C++ arrays have no such issues, so it is natural to use those in C++ code rather than messy C-style arrays.
Arduino is not limited to 8-bit AVR microcontrollers. Even if you're using an AVR, it's just 10 lines of code.