Without a SW, LE may only inspect locations, with the owners permission, and only allowed to do a cursory search at best. They are not allowed to move things over to inspect what is behind, cannot open drawers, cupboards, etc. ONLY what is in PLAIN SIGHT is allowable as possible evidence.
With a SW, LE is able to tear apart a place, car, home, whatever, and take anything that is DESCRIBED within the bounds of the SW.
I know it seems like a waste of time and valuable time at that, but it's the way it is. I've seen LE stand outside of a house where they know there are dead people inside (they could see them from the window) and they had to wait an hour or two before they entered, to get a judge to sign a SW.
Heck, in the Peterson case, LE stood outside the infamous warehouse where SP had his business, to insure he didn't come and move things before they got their signed warrant from a judge. (LE didn't think to SW the business until they got word that SP was moving things between the house and the warehouse early the morning after Laci was reported missing).
hth,
fran