Yes seriously, that's a good observation.
Even here in my village, that practice is still going on.
They actually do it as a rotation farming.
whereby, when a portion of land is planted this year, it will be left for another seven years before it's planned upon again. During that period, other portions of land are also treated same.

I can't really tell why they came up with this idea.
But I understand that they actually wanted the soil regain it nutrients again.