What is error prone about a switch? You mean you turned it on when you did not intend to or you did not turn it on when you were supposed to?
Forgetting to turn it on before a job starts is annoying but its a small price to pay for some* protection against and accident like an interlock bypassed and forgotten.
Laser systems are very different than mechanical ones. Unless warned the user does not see that the laser is on and the environment can be unsafe. This is especially true of CO2 lasers.
Frankly, if I had my way… I would have a deadman switch… on a laser systems where a human could be exposed.
Done correctly the user should be warned any time the laser is on vs it sitting quietly armed. If the machine showed [blinking light or annunciator] it was on I would feel better about it sitting silently armed with the covers closed.
Laser safety systems should be designed such that they keep anyone within range informed any time that the laser is on. They also should be designed to keep the operator safe in case any element of the safety systems were to fail.
Automated systems to turn the laser on and off could be used if they did not employ electronics as they can fail to easily and are not considered safe enough.
A good resource is to examine is the federal laser class standards for system design required for a product to pass its federal laser safety classification.
But, most of these cheap machines do not meet even the minimal requirements and most makers do not spend the time to design-in minimal safety features much less consider all the safety failure modes. This is true for the laser and the HV subsystems.
*So it may be fruitless to argue if an arm button is enough better than no arm button since the user is generally not protected against laser safety system failures anyway.
Comprehensive laser safety is not convenient nor workflow efficient it does however save you sight.