President [N. Eldon] Tanner said that President [O. Leslie] Stone of the Salt Lake Temple had called to his attention the large number of marriages in the Temple and the problems involved in requiring members of families who wish to witness the marriages to remove their street shoes and wear white shoes. President Stone mentions the confusion that often develops, that shoes become misplaced and in some cases people take shoes that are not their own, etc. He wonders if this custom could not be changed and permit those who come to witness the ceremony to wear their street shoes. The brethren felt that we should continue the present rule that street shoes should not be worn.
[David O. McKay diary, Sept. 12, 1969 as quoted in Anderson, Devery; The Development of LDS Temple Worship, 1846-2000: A Documentary History, http://amzn.to/TempleWorship]