Why build a proprietary general ledger system instead of building on top of QuickBooks?

The presenter said that after the first five years of practice, QuickBooks' pricing kept increasing and felt unsustainable, prompting the decision to build a proprietary alternative. The presenter said they are happy with that choice, haven't had issues, and don't miss QuickBooks. As a practical matter, the presenter said they don't take on business clients that insist on using QuickBooks -- clients must use the firm's in-house product, which the presenter framed as also helping with client retention.