Another aspect is the size of the business and the related dilution of power and responsibility.

Repaying technical debt in production software means introducing new bugs, instability, change. Users will have to adapt, business KPIs will suffer. The upside won't be visible. No sane middle manager would agree to that, because this will negatively impact his career path.

As a solution, I advise organizing work in maintenance teams rather than by project. Having personal responsibility for each feature or process or product also helps.