When speaking of any equipment, we do need to adapt things to fit what we each have in our personal situation. Some lucky folks don't even need heaters!
But there is a great deal of difference in how we need to deal with heater failures in many of our tank situations. Two things happen to heaters and I find they are somewhat more reliable than 40-50 years ago as things do improve slowly. But they still can stick on and overheat or break down and fail to heat, each of which is not good but the most danger comes from sticking ON.
We tend to be trained to worry about the heater failing and the fish get too cool but it is far worse when they get too hot. Two big items most of us need to be aware of are how fish are effected when the heater doesn't work right.
A tank with broken heater will cool but it is often a pretty slow process as the tank temp and the room temp is often not that far different. A 76 degree tank in a 70 degree room, will cool but slowly. Not good as the fish may thing be stressed and need treatment/meds, etc.
A tank that has a heater stuck in the ON position will often heat quite quickly as the heater is often way oversized if the suggested sizes are used. I've lost three tanks to stuck heaters and I can vouch for how quickly it happens! A 50 watt heater can totally kill a ten gallon tank in less than 6 hours! I now worry little about a failed heater as it gives me a pretty long time to notice and correct plus I can almost always treat any fish and not loose them if they do get cool enough to bother them.
However, I now use the controllers to assure myself they are not overheated as it happens much quicker and is much more deadly. Warmer/hotter water, does not carry O2 and fish die very fast. No meds to treat dead fish!
The Inkbird 308 is my ( more expensive) choice for the high value tanks as it gives me alarms for high and low. But the lower value folks get the much cheaper controllers off E-bay that do not give me audible alarms but will cut off power to the heater if it goes too high.