Why do so many men in paintings and pictures from the 19th century have their hands inside of their shirts?

by elephantofdoom

Here are some examples.

JosephWilliamNamath

Not to discourage other answers, but you may be interested in /u/LadyVagrant's response in this thread:

Why was the 'hand tucked in the shirt' pose (think Napoleon) so popular in early photographs?