Many teachers are reluctant to try new things. Sometimes it's a bad case of "I'vealwaysdoneitthisway-itis." Sometimes it's not being comfortable with the new way or not having the time to develop whatever happens to be needed for the lesson and sometimes it's even coming from a good place. What's that good place? Concern - if I try this new way and it doesn't work I'm going to lose some students and never get them back.
Earlier today I saw a facebook post asking for thoughts on teaching sorting. The question was specifically not about motivations like having the class act out sorts or sort cards but rather about the coding. I've been meaning to write about this since last summer when I attended Owen Astrachan's talk on the same subject. Early in my career when teaching sorting I developed the n^2 sorts as standalone routines just as they're presented in most books but as I gained more experience as a teacher, I changed it up to build the sorts (at least some of them) from existing concepts.