"proper" use of jumper cables

[Tobiasly]

In more English terms, the last contact you make is probably gonna spark. Better for that to happen away from the battery, where an explosive hydrogen cloud could conceivably exist.

I'd bet the reason almost no one does it is that red to red, black to black is easy to remember. Live red to dead red, live black to dead ground is not as easy.

Considering how well-made today's batteries are, I'd say the likelihood of the battery blowing up is far lesser than the likelihood of your average driver forgetting which color goes to ground.