That's because blowing up asteroids is sexy, but hardening the grid is work.
You can't make a movie out of the latter, so nobody cares.
See, also, why people love sexy non-solutions to problems we don't have (let's colonize Mars), but turn their noses at solving real problems, which affect billions of people (climate change). You can't make a slick film about a superhero convincing people to cutting back on their energy use, and to carpool, or bus to work. It's not sexy.
You can't make a movie out of the latter, so nobody cares.
See, also, why people love sexy non-solutions to problems we don't have (let's colonize Mars), but turn their noses at solving real problems, which affect billions of people (climate change). You can't make a slick film about a superhero convincing people to cutting back on their energy use, and to carpool, or bus to work. It's not sexy.