From top of my head, I can count 5 things I've purchased only after seeing an ad for it, that have improved my life immensely, solving issues that I'd never thought I had. One example is (be careful, I'm advertising here on someone's behalf) bellroy wallet. They aggressively advertised for a while. I bought one and I've kept it for years. Before that, I was purchasing one every half year and found no pleasure in using any after few weeks.

So, I don't believe that I should buy things only when there is an existing "need". Just as is the case with science and technology.