First, there's almost never an "always" in casing! Things are very much case-dependent and you have to use your business judgement!
That being said, yes, in general, when entering a market, you do need to understand the market! So, at a baseline, you do need to understand if it's big/growing (i.e. if you should even be there). Furthermore, within the market, you need to understand how different sub-markets, demographics, etc. are working in order to make a better decision!