Why is it so important for your ads or tweeted URLs to direct traffic to a relevant landing page rather than a home page or generic products/services page? Because the majority of visitors will click back or away if the page is not directly relevant to what they’ve searched for or what they’ve been promised.
Let’s compare it to shopping in the real world. In the real world I see a purple shirt in the window that I like, or perhaps I purposely go shopping for a purple shirt. I go into the store and tell the attendant that I want to see the purple shirt that’s in the window or if they have any.
An attendant with poor customer services skills will wave a hand vaguely and say, “They’re over there.” (Equivalent to landing on a home page).
An enterprising staff member might take me to a rack of green shirts that the boss wants shifted. (Equivalent to landing on a generic products page.) Selling a green shirt will make the boss happy, but I the customer am very busy and don’t have time to look at green shirts; I need a purple one. I will assume the staff member is either not interested in meeting my needs or is colourblind.
An attendant with good customer service skills will take me straight to what I want. Then advise me of the different size options. And perhaps even suggest an accessory. (“Do you want fries with that?”)
Help your site visitors find the purple shirt by directing them to exactly what it is they are searching for.