Even well-known product lead companies like Atlassian employ sales reps, especially at the enterprise and strategic levels, because demonstrating value to the end user is only a part of the sales process. There's lots of additional work that's closer to project management that's required to close a deal. It's identifying and aligning stakeholders, helping to justify budget by putting together a business case for leadership and finance teams who won't directly interface with the product and need to be sold on it's value. This is the sort of thing high level business to business sales reps spend a ton of time doing.
Huh? You absolutely still need sales people even with a market leading product. It sells itself, sure, but someone needs to work with the client and close the best possible deal.
