Because buying a home can be pricey, you want to ensure you receive the most terrific bargain. When you purchase without an inspection, you're making that decision with less information than you'll ever have again about the property.
An inspection isn't about killing deals, most homes pass with a normal list of maintenance items. It's about making sure the decision you're making matches the property you're actually buying, not the one in the listing photos.
It also protects your negotiating position. Findings can support a credit, a repair request, or simply confirm you're comfortable moving forward as-is, all of which are stronger positions than finding out later with no leverage left.
In a fast market it can feel like a step you can't afford to take. In reality, it's usually the one step you can't afford to skip.