Standard procedure for gormless politicians is to tax by stealth. If it's a choice between an efficient, equitable, explicit tax and an inequitable, inefficient, hidden tax, they'll tend to go with the latter.

So it is with infrastructure levies on new housing. Occupants of existing housing adjoining a new development won't use the parks and the new, improved public transport? The value of existing housing won't be increased by its proximity to better services?

The political benefit of hitting buyers of new housing and leaving privileged existing home owners untouched is that it fulfils Colbert's maxim that "the art of taxation consists of plucking the goose so as to obtain the most feathers with the least hissing". (That's Jean-Baptiste Colbert, not Stephen.)

An infrastructure levy of, say, $20,000 on new housing will be built into the asking price and not noticed by the geese. Applying a $2000 levy to existing housing will indeed be noticed and provoke hissing.