While not an explanation for all women, considering the percentage of women who are sexually assaulted, the IUD can provoke fear, anxiety, stress, etc. Some women don't feel at all comfortable with anyone but their husband down there, and even then it's not a gimmie that they're comfortable with their husband at first, if their anxiety approaches PTSD level. The very effective implant (into tissue of the upper arm) is just as effective (or trivially more or less so) than an IUD, but has the potential to provoke less anxiety.
That being said, I'm sure that the implant use is still pitifully low compared to less effective methods like the condom.
That being said, I'm sure that the implant use is still pitifully low compared to less effective methods like the condom.