Watch the video. It explains how Destiny actually makes use of operant conditioning to encourage you to buy each DLC and expansion.
If you are unfamiliar with the techniques of operant conditioning, here is a link to explain it in some detail.
http://m.simplypsychology.org/operant-conditioning.html
Edit: Thank you to Bant Spider for the video.
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Oh no you mean a company that wants to make money has found a way to trick your brain into buying more of their product! Whatever shall we do! We must stop this practice of businesses making money and make everything free!!