Theft?

My son graduated to the mobile phone holding majority when he started high school in September.
On Saturday he admitted he had lost misplaced his mobile.
It led my husband and I onto a discussion about bullying and theft.

I seem to have managed to get this far in my life without knowing about certain aspects of things.
I have to admit to shoplifting in my younger years, but it was for limited reasons.
A) I needed it (Not wanted, needed. Like when you are living on the streets and you NEED feminine hygiene products)
B) I knew someone else wanted it and I could profit from the theft without having the item in my posession for long.

It was only during this conversation with my husband I discovered that sometimes people steal things to PREVENT someone else having them.

What is that all about?

I understand jealousy, but thought that if someone coveted something, and then subsequently stole it, it would be to gain ownership themselves rather than purely to deprive the original owner of their property.

What possible goal can that achieve?