Yeah, those are built assuming that you're plugging into a random 15-amp circuit at the Senior Citizens Center of the VFW Hall. Their's little reason to make them capable of 20 amps because it's hard to find 20-amp circuits in the wild. Also, even on a 20-amp circuit....with the 400 foot long DJ snake you shouldn't be using the full breaker capacity. Actually, even in ideal conditions....NEC "recommends" that you only use 16A on a 20A circuit. (80% load rating).
It's one reason I use these boxes....they have a built in 15-amp breaker. To give you more local control of the safety setup. Because you
KNOW the VFW long ago changed their old-ass 10-amp breakers to 20-amp breakers to accomodate those rock hippie bands. Without upgrading the old-ass wiring to match. Or the outlets. So......
And thinking of what ops do (but never a collector, right?)...
If the main line fuses are replaced with 1/4" bolts then bad things happen. There's not much that can be done at that point. The insulation will melt and the wires will probably catch fire.
And as a serious side note:
A breaker is designer to happily pass its rated current forever, until something downline burns up. And all magnetic breakers will actually pass MORE than their rated current for a decent amount of time before they trip. For example, a Square D 20-amp breaker will pass 40 amps for almost 10 seconds before it trips. It will pass 25 amps for 100 seconds. It's something to remember!