Even if everyone serves the full three years, the free labor could be used for numerous other things, including paving roads, hospital services …
Ehud Barak made this argument years ago.
If much of the government expenses are covered by chariedi workers it can save the government a fortune in terms of transport, health, and education.
As GG, i am not coming to justify lapid, or even to ignore that much of their rhetoric is simply anti chareidi, i am just answering the op’s question.