Ann: Quarterly Activities/Appendix 4C Cash Flow Report, page-39

I think the one of the primary drivers is EOFY budgets with companies/govt spending what's left in their budgets.

I've worked in a number of govt departments over the years and they usually do their best to use up all their budget as the financial year comes to a close. If they come in under budget the beancounters will likely say "Oh then you don't actually need the money we allocated last year" then they reduce that departments budget the following year.

Use it or lose it.