Because in some places, there are taboos about burning Paper Money at crossroads.
The customs vary a lot. Wen Yan is at least an employee of the Funeral Home, so he's looked into this before. Later he's met so many Ghosts and talked with them about related things.
In the Northern Divine Land, from the mythical era onward, it's been fight fight fight, all the way fighting for thousands of years. Only in the last hundred years or so have things mostly calmed down.
But customs get cultivated over such a long time; they're not that easy to change.
People aren't easy to change, and Ghosts aren't easy to change either.
So when you burn Paper Money at a crossroads and draw a circle, that offering is specifically for your own ancestors. And according to habit, when you're commemorating your own ancestors there, you'll also burn some Paper Money outside the circle, for the lonely wandering souls.
