Why not just extend HoneyBook or Dubsado for account management after the sale?
Because HoneyBook and Dubsado were shaped for the new-business motion that ends at contract signed. The post-sale rhythm is a different shape: a monthly retainer burn tally, a renewal clock on a 12-month cycle, QBR touchpoints every quarter, expansion signals surfacing in offhand client comments, and a referral ask on the warm moment. You can bolt a few custom fields on and some AM teams do, but the result is a contact view the AM lives in and the retainer burn still lives in a spreadsheet. Strkr treats the AM motion as a first-class surface with its own objects and its own pipeline, on the same record the new-business lead closed on, so the handoff seam disappears without a second tool.