It's a waste of money unless you need it. And sometimes it's a waste of money when you do need it. There's no guarantee that they will be able to send someone within a reasonable amount of time.
We used, or rather tried to use, Good Sam Roadside Assistance three times. The first time we waited over two hours before they said they couldn't find anyone that could change our 5th wheel tire at any time soon. We gave up and I changed the tire myself. The second time they found someone that could change a bad valve stem, and they finally showed up around 10:00 pm, after being called at 6:00 pm. Strike two. The third time they were sad to inform us that all tow services were too busy to help with our stalled, out of fuel due to faulty fuel gauge, truck. I was able to get fuel, crack the lines to bleed out the air, and got back on the road myself.
So my experiences with roadside assistance is that it's a waste of money. YMMV.