What can the reader infer from the question "When did you learn to write by hand?"?

From the text, we can infer that writing by hand has become obsolete. Technology is the main form of communication and the written word, making it all the easier for one to be spied on (hacked).

“What’s this?” Tally opened it up and saw a scrawl of letters. “When did you learn to write by hand?”
“We all learned while we were planning to leave. It’s a good idea if you don’t want minders sniffing your diary. Anyway, that’s for you. I’m not supposed to leave any record of where I’m going, so it’s in code, kind of.”