We're all creatures of habit and what we type into the search boxes isn't random, it's influenced subconsciously by our language and culture. Our searches follow certain patterns, we share the same types of words, we're influenced by news stories and the latest buzz or fashion.
Many online marketers make the mistake of only doing keyword research at the start of a project. That's a mistake because people's search behavior changes over time. New products and new fashions emerge and with them, different keywords. These are opportunities you can capitalize on.
Keyword research is an ongoing process that you should build into your weekly schedule. You'll gain a deeper understanding of your markets, you'll spot emerging trends and new profitable niches before your competitors.