Ooooohhh, that's a loaded question! There are a few Tada-san interviews that might give you an idea of the original intent from the Chief Engineer himself.
I'll try to sum it up in my own words...
There's no specific 'event' that it was made for. It'll drift, it'll grip, and it'll carve up canyons. I think the point of this car was to reintroduce the desire to do all those things, in a world where most people can't sacrifice the time nor money to buy a modern performance car, or perhaps buy a car from the 80's or 90's and have to deal with the impracticality that older cars might involve.
It tries to incite the joy of driving, while trying to keep sacrifice to a minimum.
Idk if that makes sense, but that's it in a nutshell...
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"Sweet Subaru, sweet Subaru, send your BRZ unto me, for the roads of the unworthy must be baptized in speed and glory."
- The Ancient BRZ Sacrament by Zaku