What's so bad about no marketing? I've got a chip on my shoulder because we severely disappointed customers by shipping a product that lacked tons of features

What's so bad about no marketing? I've got a chip on my shoulder because we severely disappointed customers by shipping a product that lacked tons of features that marketing had hyped up beforehand. Most of their ideas to win back customers were good in spirit but were bogged down by banal details and deceitful trial terms / payment rules. I fully accept the idea that this is just an example of terrible marketing and not representative of marketing as a whole, but I haven't got a personal experience of marketing being a huge boon. I can't say I'm a good example because the end users of my code are company employees, I make internal tools, but even then we try to set our own deadlines and keep them with no external dictation of when stuff must be done.