Creating custom events is important for:

Custom events are crucial for understanding user behavior and tracking conversions because they allow you to define and measure specific interactions that are not automatically tracked by GA4. This includes actions like button clicks, video plays, form submissions, or specific content engagement, which directly indicate user intent and progress towards a goal. By tracking these custom events, businesses can gain deeper insights into how users interact with their site, identify friction points, and accurately attribute conversions to marketing efforts. Measuring page load time is typically done with built-in metrics or specialized tools, not custom events. While custom events are essential for tracking many conversions, it's incorrect to say conversions can't be configured without them; some conversions (like page views) are tracked automatically or via enhanced measurement. Custom events do not directly avoid cardinality issues, which relate to the number of unique values for a dimension.