I thought the point of an advert is to inform you a product exists and if you need it you can buy it
The point of advertising (businesses only) is to improve profits by improving sales. Yes, information may be a part or all of an ad: "Garage sale here this Saturday at 9AM."
Also, we see language that manipulates with imagery, often misleading, like the smiling, sexy model selling cars or people using a product shown beaming with happiness, as well as verbal imagery: "Rich buttery flavor."
There may also be indoctrination - repetition resulting in the passive reshaping of thought and desire: "Winston tastes good like a cigarette should."
And yes, people are very manipulable. Therein lies the power of critical thinking. Learn how to evaluate the speech in advertising and reduce it to the information component and make decisions on that alone. That doesn't mean that you might not be shown something that looks good, want it, and go purchase it, but we don't want the advertiser creating that state of mind in us unwittingly. The value of critical thought is not in accumulating demonstrably correct beliefs while avoiding false and unfalsifiable ones, but in the application of that knowledge to optimize experience, and the false promises of advertising generally lead to disappointment.
Consider these words in that context:
When I'm driving in my car
When a man come on the radio
He's telling me more and more
About some useless information
Supposed to fire my imagination
I can't get no satisfaction
'Cause I try, and I try, and I try, and I try
I can't get no, I can't get no
When I'm watchin' my TV
And a man comes on and tells me
How white my shirts can be
But, he can't be a man 'cause he doesn't smoke
The same cigarettes as me
I can't get no satisfaction
I can't get no girl reaction
'Cause I try, and I try, and I try, and I try
I can't get no, I can't get no