This is by design and it's a good thing. If every salesperson is allowed to drop high priority "but my client is asking for this NOW" work items on engineering,

This is by design and it's a good thing. If every salesperson is allowed to drop high priority "but my client is asking for this NOW" work items on engineering, you'll end up in a tug-of-war of competing priorities from O(n) stakeholders who don't give a shit about planning or roadmap in order to make their sale. Been there, done that. A proper product owner can balance all such requests and figure out what actually is needed to move the product forward. Salespeople need to make a business case for getting their requests done. Potential monetary results alone is often not enough, for good reasons, to force a context switch in an engineering team.