Because that's what "overcollecting" the payroll tax amounts to. Certainly the effect is identical to a tax hike:
“If they're looking at reducing the deficit by increasing the premiums...it will slow down the hiring process,” Mr. [Jason] Myers [president of Canadian Manufacturers & Exporters] said.
In fact, it appears that Jim Flaherty will rely almost entirely on an increase in EI premiums to bring the country out of its current deficit position. That's it. There's nothing else in Thursdays economic update that could be accurately described as an element in some deficit reduction plan.
Interesting to see the NDP response to this going forward. Jack Layton seems willing to wear the purple sweater, to "make parliament work", as they say, in exchange for some tiny little political bone related to changes in the EI system. An increase to the payroll tax was precisely not what he had in mind.