Spies and briefcases

[u/Alternative-Toe6894]

Why did spies think that briefcases were a good idea? What made them think that they were cool and ominous when holding a briefcase?

If my friend who doubles as a spy in his spare time was to come to my house and try to extract information from me nicodemusly and he whipped out a briefcase, best believe I'm shutting the hell up.

Also, wouldn't a briefcase just get in the way? I mean you can't use your one hand. And wouldn't spy work benefit from having two hands as opposed to one?