Inga: That thing that is everywhere yet very few know just what it is.

...cause people getting turned into animals or objects happens SO commonly.

Exactly right, it's such a common happening, that kindergardeners and toddlers are warned to never go anywhere alone, to never talk to strangers, because there is a very real danger of them ending up as some item in a shop somewhere, or as a nick nack for a house.

Everyone knows about that. What they do not know is what drives people to do such actions. As a fur uses more and more magic, the Inga within them, created by their magic, will begin to grow stronger and stronger. As they strive to slake their desires, if it isn't dealt with. (By some sort of selfless action, which is anathama to a growing Inga possession,) Eventually, the inga will take over the magic user and twist their desires, so, the kindly toy maker who once made and gave out toys to the children to see them smile, might suddenly decide that it's better to permanently transform those children into nice toy's, to forever be happy little objects......and to take their magic for himself....after all, they won't need it. Once it has taken over a fur, it's impossible to remove with mortal magic, its the darkest parts of the user's soul, having taken over and twisted everything they used to be. They're still the same person in body, but in mind, they are far, far more dangerous and obsessive with their desires, driven to greater and greater heights to both slake that desire, as well as make themselves stronger.

The in universe reason is people just assume that powerful magic users are naturally corrupted by being able to manipulate the laws of the world to their whims, oh how wrong they are.

eh.... some are just as prone to just deciding they can get away with it. :P I mean look at Akanos's gallery sometime.

...or don't.