Probably because the folk religion predates the clerics as it was just there rather than spreading in from the middle east.

The Romans worked in a similar way. The senate proclaim dead emperors to godhood even though they really didn't want to do that because the emperors were usually anti-senate or the senate had even killed the emperors or Caesar in some cases.

Additionally in practice beatification in Catholicism is just an approval process where they determine that people the masses are venerating were indeed saints, so it really is just more of a case of the Church pretending like it is in control more than anything.