Candlesticks are the most widely used method of looking at financial time series data.
So widely used, in fact, that it is sometimes easy to forget that the map is not the territory. Candlesticks are just one transformation of the underlying data that happens to be easy for humans to digest. But a computer can digest the raw tick data even better than the candlestick representation.
We often think that our view of reality is reality itself. But the process of evolution filtered for survival and reproduction. We only see (and hear, touch, smell) a reality that is limited by the evolutionary need for efficiency.