How can I learn to recognize when marketing is influencing people's needs rather than responding to them?

[jayonmarketing]

I've been curious about how advertising shapes the way people think about what they need. Some campaigns help people discover products or solutions that genuinely make their lives easier, while others can make people want things they never really thought they needed in the first place. As someone still learning about marketing, I'm interested in how to tell the difference between understanding what customers already want and influencing them to want something new. How do marketers recognize where that line is?