Who are you to decide for other people what they find useless or not? And are you implying people have no free will to decide what to buy and they need others to "trick" them or to prevent them from buying?
Do you consider yourself above other people and some sort of arbiter for their decisions?
Then you should stop writing right now because to communicate is to manipulate. People are manipulating machines. Sometimes to sell useless crap, other times (just as useless) ideas and ideologies. It comes with being a human and interacting with other humans.
People should have the freedom to choose who they listen to though, instead of others deciding for them.
I'm talking about dedicated departments in large companies that try to steer people into more purchases for profit. This is unethical unless people gave their consent.
Now you are simply describing advertising. I do not find it unethical, maybe unpleasant at most. It is the engine of commerce and driving progress. It is a sign of abundance of choice. And let's not forget a company still has to create a compelling product - no ads can override my free will.
Do you consider yourself above other people and some sort of arbiter for their decisions?