I think it's the desire of all of us to have as much as we can in the main estimates, as opposed to using supplementary estimates as a tool. I think we explained the last time we were here why it's very difficult to do that.
I would point out that governments can decide--and particularly a government that has been able to manage a surplus situation, as have this government and the previous one--what to do with that funding. If they decide that instead of reducing the debt or reducing taxes they are going to spend, then that spending will need to be reflected through supply in Parliament.
What you are seeing in the last number of years by way of higher supplementary estimates is the overall growth in spending year over year, which has largely been announced in the budget and therefore not reflected in the mains but essentially reflected in supplementary (A) in the fall or the December period.
Supplementary (B) is usually quite small, and it often involves transfers between one department and another, and the like. But the large spending, the significant use of supplementary estimates, has been in supplementary estimates (A), which reflects the increase in spending as a result of decisions made in the budget.