In my case the primary benefit of a toaster is that it requires minimal intervention, not energy efficiency.

When I'm trying to get multiple small humans dressed and fed in the morning I prefer to put all the slices in a toaster oven and set the automatic timer. If I used the oven broiler I would have to manually set timers to remind me to run back to the kitchen and flip the bread. And of course if I forget or can't make it back to the kitchen in time then it doesn't take many burnt-on-one-side pieces of toast to equal the cost of a toaster.

I agree that there are niche kitchen gadgets that are not worth the space but it depends on the person. For example, I do not have a dedicated coffee machine, but many people consider theirs indispensable.