I bought a box of 500 envelops recently and made sure they were of the security variety. I send out a mass mailing at least once a month usually not containing any sensitive information but no one but the addressees needs to know anything about what I'm sending. The cost of 500 non-secure envelops was only $2 less. I also made sure the envelops I chose were self-sealing. Licking one or two envelops is no big deal but a dozen or more is time consuming and just plain yucky. Come to think of it why bother licking even one? Why do they even make the other kind?
These are envelopes. When you seal them the papers inside do not fall out. With the correct postage and a legible address you can mail them. They do what envelopes are supposed to do.