New-ish CFI here, but after about 500 hrs of dual given I find the iPad to be a HUGE distraction.. at least for people who are pre-solo. Keep your head out the window, learn the local landmarks, all that jazz. I had a few people show up early on with shiny new iPad and Foreflight they got as a gift and it's not appropriate that early in the game.
However, at least in my case we worked in Foreflight during the cross country planning phase, doing all the paper work first, then, mapping it out on Foreflight to see how well (or not!) the numbers matched. For at least my students having them see how the sausage is made was a big benefit to them.
Observational question: do you, as a CFI, use an EFB frequently while in the cockpit with a student?
If so, I wonder if there may be some transference without context occurring. For example, a student seeing your use of it equates to them just accepting the EFB must be useful, despite no real instruction from the CFI on why and how you’re using it.