I don't find it useful at all really. It's very neat but I've never had problems with the power plugs of any other laptop.
In fact I don't remember having a laptop charger break for any other reason. It's always the DC plug or cable.
I don't know if Apple hold significant patents on the idea, because I'd absolutely love to see it applied to other connectors, especially headphones and wired ethernet leads.
The benefits of the magsafe connector far outweigh the hazard in the uncommon scenario you've described. Those benefits are reaped over the entire life cycle of the machine itself. The hazard you're describing only occurs at the end of the life cycle of a relatively inexpensive and user-replacable subcomponent.
Design is very much about tradeoffs, but one would never trade off such vast benefits to ameliorate such a limited hazard.
Plus, you'd be using the hardware beyond its designed intent. This is very similar to never checking or changing the oil in your car, and complaining that the engine has seized after years of use. Just stop deferring basic system maintenance: go buy yourself a new battery!