To avoid powerful artifacts

1. Because power corrupts. How many characters, after gaining something that fills them with power, isn't at least tempted to use that power for their own gain?
2. Because it might cost you your sanity. Seriously, most characters who come across a powerful artifact are driven mad by it.
3. It could unleash an ancient evil. You would think that they would label any object that is being used to contain an evil creature. But unfortunately, labels weren't very popular back in those ancient times.
4. It could become extremely clingy. Some artifacts get lonely, and so will eagerly bond with the first person who comes along. Sadly, the artifact doesn't seem to care if its companionship is accepted by its new person.
5. It might kill you. Are you really willing to risk touching that golden scepter, which might turn you to stone if you do?
6. It is probably guarded by a dangerous creature. Or two. Maybe even three. Can you defeat three monsters at the same time?
7. You don't know who else might be searching for it. It's one thing to go after that artifact no one cares about. But when a search for it could lead to a war against the neighboring kingdom? No thanks.
8. It might not even be there. It is a horrible feeling to make it through deadly traps and dangerous creatures, only to find out that the artifact you sough has already been taken.
9. Because you aren't the hero. If the artifact can only be used by a certain person or bloodline, then why waste your time trying to get it?
10. Because you've already found three fakes. After so many false artifacts, what makes you think that the next one will be real?