This is an interesting view of Marketing - as a part of the Sales pipeline. I suppose it makes sense in that Salesforce are a lot about pipeline management but it's also pretty narrow.
Clearly, as prospects travel down the pipeline, you have an unusual opportunity to learn from real people about what is working and what is not, but it does down-play other aspects of marketing such as advertising, social media PR, Brand, and indeed Product. Getting that first interest demonstrated by a prospective buyer is surely also a marketing responsibility.
I guess, when you're a hammer, you see everything as a nail.
What happens between the first interest demonstrated by a perspective buyer and that engagement with the seller? That’s where marketing comes into play.