Thankfully we never needed it and have bought it on and off depending on what is the cost of the insurance. When we have bought it, it was always with the cruise line (never tried the independent insurers). For us it’s more about the cancellation portion prior to departure rather than the medical coverage during a cruise as my personal health insurance would cover that.
if it’s about 5% of the cruise cost, we’ll usually get it but we’ve seen it a lot higher and refused it. I realize it’s taking a chance but again it’s about cancellation cost risk and what it’s worth to have that secured