Lucy doesn't like a cat tree, she only likes destroying carboard boxes by biting chunks off and throwing them down the back of the desk in the study - she likes to sleep on the desk so she can nosy out the window at the same time.
Or she sleeps in the basket upstairs which must have a steady supply of DS2s discarded clothing. He must have a smell she likes, He can't leave anything anywhere and she is on it like a rocket - it was his bloody school tie the other week and she ripped his hands to shreds when he tried to take it back to wear to school.