Because weeds always make their way into your garden from the surface (and sometimes from below), getting to the tap roots of elm trees and bind weed is impossible and pulling weeds by hand results in pulling dirt to the surface and missing the traproot entirely thereby making an even bigger mess of weed blockers for very little return.
Cardboard mulch—On new gardens with topsoil I use cardboard as a temporary weed blocker. The cardboard decomposes in two years, killing most initial weeds and always enabling access to a weed's taproot. Additionally, cardboard enables a gardener to access underlying weeds in the interim for removal as cardboard if floating (no stakes).
Roadbase—One reason folk use weed blockers to keep the aggregate from sinking into underlying soil. I use a 1/2"-1" layer of roadbase in place of a weed blocker. It doesn't last an eternity, but does provide an alternative to weed blockers while still enabling tarproot access. roadbase also tends to minimize ant hills.
(Exception) River rock—Large river rock is useful for areas that receive a lot of errosion and water. Sometimes large river rock are magnets for weeds, grass, and other debris, and you maintain them a few times a year in order to prevent propogration of unwanted growth. In this case, 2' sections of unstaked weed blocker can speed up maintance and access.