For some luxurious goods, however, such as an expensive bag or a pair of shoes, people might purchase them because others have them as well. This phenomenon is especially common among high school female students. As girls begin to care more and more about their looks, their perspective on beauty starts to change collectively. For example, a girl who wears a pair of UGG shoes may eventually starts a trend. If her classmates think having a pair of UGG is cool and pretty, then they will want a pair too. So it is common to see within a school that girls dress very similarly with one another. This is an example when purchases are not needs, but simply because others have it and so one wants to have it too. According to a survey conducted by Trend website, a significant percentage of luxurious goods buyers consider luxurious brand as a label for their social status or wealth and they tend to choose the brand that their colleagues or friends recognize or value.
In sum, I think most of the time people make purchases because we need them, but there are rare situations where making a purchase is because others have it.