In the course of a home inspection, the inspector is looking at many components that are supposed to weep(1).
"Weep holes," as they are called in the trades, are openings that should be found at the base of all exterior siding -- including stucco, wood and composite siding, and brick veneer -- to drain away moisture that gets behind the exterior finish. Even when present, landscape grading and soil that is not held below the base of these sidings or veneer can block the weeping and can trap moisture behind the exterior finish.
The absence of these weep holes is what trapped moisture behind the EIFS (Exterior Insulated Finish System) stucco products of the 1980's and 1990's over which many class action lawsuits have been filed. The trapped water rotted away the framing behind the EIFS in as little as three years in one subdivision in North Carolina.
Another place weep holes are observed is at aluminum windows. The lower track of these windows is supposed to have weep holes facing out to direct moisture (from rain or condensation) that gets inside the track to the exterior. It is surprising how many times I have seen windows (original installations, but particularly replacement windows) installed backwards with the weep holes facing the interior of the house and even upside down with the weep holes on the top of the window.
Anywhere that condensation can occur, weeping drains are necessary. That's why a furnace with air conditioning should have a condensate drain plus a collection overflow pan under the unit with an overflow drain -- both pipes running to the exterior.
Very often ceiling stains are NOT roof leaks, but condensate stains. Homeowners will occasionally install a new roof to address these "leaks" which turn out to be dripping from condensate of the air conditioning evaporative coil at the furnace located in the attic.
Condensation also occurs in the attic on cold surfaces during the winter months. Metal pipes and framing anchors are common sources from which I have seen evidence that they were dripping onto the ceiling below. Condensate drips also occur in summer months on uninsulated A/C lines in the attic and poorly drained evaporative coils (as in the case above).
Weeping holes are also critical at retaining walls. At the base of any wall designed to retain soil behind it, the most important issue is what to do with the weight of water that accumulates there. The first sign of a failing retaining wall is efflorescence caused by water leaching through the wall. The simple solutions are either weep holes or a footing french-drain behind the wall that drains to daylight.
The footing drain is best because it is less likely to silt-up. Weep holes installed at the base of a retaining wall must be protected from silt, or very quickly (three or four years) they will become clogged. This is particularly true of the weep holes designed into masonry walls by leaving out mortar at vertical joints at the base of the wall.
Unless a home inspector is looking for the failure of weeping components, s/he is probably not well trained. To determine professionalism, try asking your prospective home inspector if his/her report addresses "weeping."