Event-driven processing is distinct from scheduled processing and consumption distribution can only be managed from scheduled processing. In addition, not every process on a system is in general written in Perl. Nor does one generally have the luxury of rewriting a system just because, say, one believes event-driven processing to be aesthetically better - that is at least how managers tend to view it.

In my own situation, the only way I can achieve a totally event-driven version of the kind of system I work on is to pay for the development myself.