In Connie Willis's Nebula and Hugo winning novel The Doomsday Book, published in 1992, there seems to be major technology discrepancies that don't make sense to me. This is a novel about historians in the year 2054 traveling back in time to study history. The modern side of this story has video phones, time travel, advanced virus inoculations, but no cell phones or answering machines.
Much of the plot in the modern part of the story is around Mr. Dunworthy trying to get ahold of certain important people, yet he is unable to leave any messages or call a cell phone. The car phone was already common in 1992, and cell phones were beginning to be common, albeit in a briefcase size, but it doesn't take much imagination to see them miniturizing.
Why did she make these decisions to exclude currently existing technologies in her time (cell phone and answering machine)? Was it just a plot device or am I missing something?