for your security
McCaughan's Law of Customer Centredness: Whenever any measure is described (by a corporation to its customers) as "for your security" or "for your convenience" or anything of the kind, the real reason for the measure is "for our profit margins" or "for our convenience".
Case in point: on aeroplane flights you're likely to hear some spiel along the following lines: "Attention, please. Here is an important security announcement. For reasons of security, you must remain within the class of seating for which you hold a ticket. If you attempt to enter any other class of seating, our staff will direct you to return to your own class. Thank you for complying with this important security measure." Security. Ri-i-i-ight. Real reason: maintaining the distinction between seating classes, so as to increase the feeling that the more expensive seats are exclusive and desirable.