If the student wants to learn something like phrasal verbs, prepositions or basic grammar I sometimes give homework so they can continue learning/practicing  after class if the student is okay with that. 

I always give homework. My students are adults, they invest their time and money in the learning process and they understand that doing homework will maximize their results and will help them achieve their goals faster. Yet this is their choice if they want to take this opportunity to do it or not. Usually, they do. 

I do sometimes. I generally give writing homework to students that mention that they enjoy writing. So I give them the option of a writing assignment. 

I give beginner students homework if they ask for it.  Also, I teach writing so sometimes the student write things and send me for corrections.