I understand what you say, up to now we have traveled with it on but recently questioned it.
Then we read a few articles that exacerbated our feelings so I guess now we're a bit apprehensive about traveling on interstates and through tunnels with the propane on. We're just not sure about it.
And a few professional reasons:
As an engineer I understand that all systems, no matter the design,
can fail, and as Murphy's law dictates - at the most inopportune time.
As an EE I feel more comfortable with electricity than fire.
And a backup system is not a bad idea anyway.