I often hear people using the phrase "out of courtesy". My question is: can we also say
- out of honesty
- out of simplicity?
If not, then why not?
Indeed you can use it that way, although it's rare.
"...pay your tithes and offerings out of honesty and integrity because they are God's rightful due."
"I was too scared to tell Dada that I had confessed less out of honesty than out of the fear of being found out."
You can also use "out of pity", as in the folk song, "Take Her Out of Pity"
"Come a landsman, a pinsman, a tinker, a tailor,
A doctor, a lawyer, a soldier, a sailor,
A rich man, a poor man, a fool or a witty,
Don't let her die an old maid, but take her out of pity,"