Yes that's been the problem. Duo works well for video chatting and my husband and I used it between us for the months we were exclusively on Android.
We get people who nod and say yes they will install it and then never get around to it. These are family members. I would not dare try and impose on the parents I have to text with, when their kids are under my supervision. I've exchanged SMS texts with a few of them when I was exclusively on Android, but it was hit or miss as to whether they would respond in a timely manner. It seemed the green text bubbles confused them or something. I don't know.
There's a limit to how assertive either of us can be about it, which is not very. I know I would not like someone hounding me to load apps on my phone. Goodness knows how hounded I was to get onto Facebook and how much I resented being on it until I had enough and left FB completely.
We tried an app called Wire that's encrypted but the video portion of the service just wouldn't work for us for some reason.