Most people don't have a system for finding events. They have a few default sites - Time Out, Dice, maybe a venue or two. Checking those feels like checking what's on. In practice it's checking the few places you happen to know about.
Different kinds of events live in completely different places. Gigs are in one ecosystem. Kids stuff in another. Talks, food markets, local community events - each has its own scattered set of sources, and a lot of the good stuff never makes it onto the big platforms.
You do come across good sources over time. Someone sends you a niche listings page. You find a local site that's great for family activities. You discover a venue that consistently puts on good nights. But there's nowhere to keep that knowledge, so next time you fall back to the same defaults.
Your map of where to look never compounds. Even though you've actually learned much more than your default sites, you can't access what you've learned. You keep starting from the same narrow set of sources, every time