[jvandonsel]

Well, one could argue that spreading humans outside this single planet is a requirement for long-term survival of the species, and thus as important or more important than those other causes you mention.

I don't personally subscribe to this belief, but many people do.

[drakonandor]

The primary obstacle of the "real problems" mentioned is people.

For example, consider that:

Sometimes people don't want to be helped (see: many homeless)

Sometimes leaders don't want their people to be helped, because they gain from keeping them down (see: African warlords / government leaders embezzling aid)

When faced with SOCIAL problems like these, it's no wonder that someone of a 'hacker' mindset like Elon instead prefers to devote his time to solving problems which instead have technological roadblocks (well, maybe not entirely applicable in the case of Tesla or SolarCity).