This was really interesting and, well, I'd never really thought about TW this way before. The most I went about caring for the "other people" was wondering why people didn't react to the sleeper agent mum letting her pram trundle off.
But then again, this is quite the norm with entertainment of the 'hero' genre. Despite the fact that these heroes exist to save people, in the end, it is always easier to both portray and feel for the heroes more than for the people who are collateral damage. Also, for a show that is 40 minutes long, it is easier to focus on the main characters than on peripheral ones that may never turn up again.
Though the writers could have tried to make us feel for the 'other people' through the reactions of the team to the destruction around them (that's kind of Gwen's role I guess, though her 'humane' focus is often quite selfish), in the episodes where there was a high body count, TW itself suffered loses, so their loss comes to the forefront again. And as for the episodes with lower ones... well, it's pointed out quite often that TW has the tendency to be quite callous of the deaths of the 'ignorant' masses.
Yeah... anyway, that's my opinion on the matter. It would be great if we could debate this or something. :) Thanks for bringing this up.

And we've always got fanfic to make up for what canon lacks. *feeds plot bunnies too*