>If your customer wants your product then by definition you don't have to sell them.
That's a misnomer, what if they don't know you exist? That's what sales and marketing are for, to inform people that could benefit from your product that it exists, essentially. Will their business implode if they don't buy your product? No, almost certainly not. But, they might derive a massive cost savings, time savings, increased employee satisfaction, or other efficiencies by using whatever you're selling and your job in sales is to get them to listen which is the hard part.
This is a fiction that salespeople tell themselves to help them sleep at night. I use twitter not because someone from Twitter Sales sold it to me but because I sought it out of my own volition.
Only bad products need sales. Good products can thrive on marketing alone because people want good products.
I quit that job as soon as I could because I was sick of manipulating people or pressuring them into buying something they didn't want. At the end of the day that's all sales is. If your customer wants your product then by definition you don't have to sell them.