This is a relatively modern phenomena, a by-product of the age of porn. The obsession with sending nude pictures is a modern one.
Long-distance relationships weren't uncommon, especially during wartime with deployments.
I have spoken with many women who have used online dating and they are bombarded with creeps asking for nude photos. Mind you, some of these women are in their 40s.
The closest thing to nude pictures were glamour shots; photography studios would take provocative lingerie shots for women to give to their boyfriends/husbands, sometimes as a birthday or Christmas gift; a couple episodes of Cheers had them (Lilith shows a large one to Frasier and says, by the way, here are the other pictures),