Why marketing/promotion isn't important when it comes to the product lifecycle?

No, I am not trying to be controversial but trying to explain why we are able to hear more about promotion and marketing activities more than other parts of the cycle.

By other parts, I meant to say product, place, price and topic under discussion promotion.

The answer to why is something all of us have already been acquainted with. For eg. when you go shopping on an e-commerce site you search for a specific product, then you check if the product is deliverable to your place and then you check if that product is economically sensible. So it's simple the dependency looks like this product>place>price>price.

So why do we hear more about marketing and promotion activities?

The reason being turnaround time or affectionately TAT. Promotion can be structured and altered briskly when compared to other p's.

Well I could sate and quote a few regressions or projections but it makes sense to grasp this on your own as you would be your best teacher (Not that I don't have any links to attach)

So what I meant to say is not that promotion/marketing activities aren't important just they are an extension of the other 3 p's.