In a start-up company situation, there has to be some modicum of predictability in order to have "helpful" predicted limits. The math of SPC gives us a way to judge whether a process is "in control".
Statistical Process Control limits can show expected ranges for process metrics. It is helpful to know what is expected, so to recognize and react when the process behaves unexpectedly, both in a favorable and unfavorable direction. Planning and budgeting for a stable, predictable process is far more reliable than for operations which are not in a state of statistical control.
Where your team is working to improve quantities with negative consequences, such as complaints and DPPM, it is helpful to judge whether minor month-to-month improvements are large enough for the team to take credit, or whether the minor improvements could just as likely be random month-to-month fluctuation.