People often say will why did that person get addicted and the other person didn't (or develop PTSD from a chaotic family atmosphere one sibling does, one doesn't) because they are different!

As for the reason why people choose...it always starts out with a pleasurable reward. Rarely does one notice it is happening, that it is turning into an addiction - until it's too late and they are hooked. One of the sections of the post I posted this morning touches on this and I included a 10 min TED talk by a psychiatrist who argues that mindfulness meditation to aid in changing bad habits makes us curious which provides a reward. You may be interested! It's not hard to find on the page it's the youtube video :)