Maybe you have the prettiest house on the street. Or maybe your place is so tumbledown that you're worried the town will condemn it or fine you. But if somebody in a car pulls up to your house, snaps a picture and leaves, there are other more likely reasons other than admiration or condemnation.
The mortgage broker will nearly always send an appraiser to evaluate a home the company is considering financing. Part of the appraiser's job is not only to photograph the subject house, but other houses in the neighborhood that are comparable, meaning they are approximately the same size, age and condition. If you bought your house less than a year ago, it's a good candidate for an appraiser to photograph.
Though the broker may have already supplied bank underwriters with an appraisal and photos, underwriters are exacting and may ask for additional documentation, which can include additional pictures of current comparable homes.
If you are in financial trouble and having trouble meeting your monthly mortgage payments, the bank that owns the mortgage will send a real estate agent, appraiser or local loan officer to photograph it once foreclosure proceedings have begun. If you are still in the house, they usually only photograph the exterior.
If you refinance your house or take out a line of credit against its value, it is likely that the mortgage brokerage will again have to provide bank underwriters with photos of it and comparable houses nearby, even if they don't ask for a full-blown appraisal. These are called drive-by appraisals.