If you have ten engineers and even just 100 customers, you have a very high number of conversational edges. Good luck keeping things consistent and doing any sort of long-term planning if engineers are turning the output of those conversations directly into features. "Engineers talking to customers but not making any changes" would be more stable, but is still a very expensive/chaotic way to gather customer feedback.
Additionally, very few of those single engineers have a full knowledge of the roadmap and/or the ability to unilaterally decide direction based on some of the customer feedback or questions. "Will this get fixed in the next two weeks?" "Will you build X?" etc. You don't want your customers getting a bunch of inconsistent broken promises or wrong information.
The best-managed orgs I've seen have pretty heavy engineering and user experience in their product and support orgs. You need people in those roles with knowledge of both how it's built AND how it should be used, but you can't continually cram all that knowledge into every single engineer.
A startup should start with the builders talking directly to the customers. But at a some point, if successful, you're going to have too many people to talk to and need to add some intermediaries to prevent all your engineering time going to random interrupts, and centralization of planning responsibilities to ensure someone's figuring out what's actually the most important feedback, and that people are going to work on it.