Hobson’s choice

English expressions are always interesting. I like the explanation on Wikipedia «A Hobson’s choice is a free choice in which only one thing is actually offered. The term is often used to mean an illusion of choice. The most well known Hobson’s choice is «take it or leave it.» I heard this expression once in a podcast. Since then, I can’t forget. Why is it so hard to learn specific essential phrases and the unimportant ones we always remember?