One point would be the racism and prejudice factor. Selling a product to low wealth blacks by connecting to them through slang and using the imagery of middle wealth blacks. Buying such product can make you feel better.
McDonald's would use ads like this. If you eat here you feel like a better person. You share a table with middle to upper wealth citizens, yet its affordable to lower wealth blacks. I don't remember the the slogan, but it was definitely directed towards inner-city families.
Also when specific restaurants placed ads with only white people in them eating and enjoying themselves. Non inclusion of blacks can create a safe haven for whites to go out to that place in comfort.
Women were never portrayed into advertising for heavy equipment or large trucks, because there was a sense in masculinity for such products.
Now as time has changed these things have began to phase out. Women are riding lawn tractors, young kids are in mixed social groups hanging out and enjoying themselves at McDonald's. 20 or 30 somethings are getting high on life at Applebees with multiracial associations and friends.
You even see high end jewelry companies utilizing blacks as the wise ones looking over the young white couple on their engagement.
In short, advertising has less segregation due to race age sex or upbringing. Its not completely gone mind you, but successful ad agencies are using less of these attributes to sell products. Advertising is a reflection of society, otherwise you can't sell a lawnmower to sexist pigs (So easy to operate a woman can do it= not manly enough).
Small business ads are also changing. People who would prefer to buy local pay attention more to those than big business. Another point would include environmentally conscientious advertising. Selling products with this in mind helps.
Also using confusing words like virtually and nearly are coming up more frequently. Confusion at consumers seems to work well.