What is the importance of demographic and psychographic information in developing marketing communications?

What is the importance of demographic and psychographic information in developing marketing communications?
Well that is not necessarrilly the question you should ask. Instead you want to know who will you be selling your product/ service to? If you run a tax business your demographic is large when it comes to age of customers; however breaks down from there. Younger people will have a very simple return, they do not yet own a house, probably do not have stock, only 1 or 2 bank accounts. On the other hand older married couples they do have a home, have a pension, draw social security. Middle age families you can claim earned income credit, several dependents.
So a marketing scheme that seems easy tends to be far more difficult when you enter into the aspect of demographic marketing, you cannot just make a commercial saying "we have trained professionals completing your return for affordable prices". You need to show all of these different types of peiople using your business, ensure families you get them all they deserve, ensure young individuals that they have no tax liability and should always file because it is worth it considering the paid some taxes in the year, and lastly ensure the elderly you will take care of everything for them and that they do not need to worry about a think because they do not want to.