I think it's simply out of fashion. E.g., "Don't mess with Mr. In-between" is a line from the 1940's song "Ac-Cent-Tchu-Ate the Positive." It's addressing abstract entities in a personalized form, which --I assume-- is a style convention commonly understood at the time.

https://www.youtube.com/watch?v=5Qk9o_ZeR7s

https://en.wikipedia.org/wiki/Ac-Cent-Tchu-Ate_the_Positive

I learnt of this song through the fantastic series "The Singing Detective."