I never worried about insulation types until a job almost went up in flames.
For years, I figured if a cable worked, how it was run didn't matter much. Then, I did an install in an old house with flammable insulation. I left some wires loose near a heat duct to avoid extra work. A few months later, a fire started from overheated cables. Thankfully, no one was hurt, but it scared me straight. Now, I never cut corners on safety specs, even if the customer pushes for a cheaper fix. That risk isn't worth saving a few minutes. My whole method changed from getting it done to getting it right.