Why don't they marry a foreigner?

If they still actually use dowries, what makes you think they are at all willing to break with tradition and allow their kids to marry with a foreigner?

Foreigners are different and not good. They don't know the language or the culture. Letting your daughter marry a foreigner, you might as well let them go and leave the country and never hear from them again. Plus, you could never be assured that your son-in-law is a good, upstanding person, because a foreigner exists outside of the system. You don't know who his family is. And that's besides the point of different religion.

And if everyone else's daughters are getting married with a dowry, and you give your daughter to someone who doesn't ask for a dowry, isn't that shameful?

I have absolutely no authority on this issue. So, take my answer with a grain of salt.

OR they could just let their daughters marry for love like the rest of the developed world and not involve a dowry at all, like the rest of the developed world. If something is causing that much of a problem to where murders are taking place, they should take it upon themselves to do away with such an old fashioned practice. But as far as I can tell they are morons.

Because a foreigner may not want to live in India, and the Indian girl may not want to live in a place where she'll only see her family once a year, if that?

Moving away from the country one grew up in, and away from a culture one is familiar with, is a big deal. I work with people who have done that: it takes a huge leap of faith to immigrate and decide you may never see your family again.

Your speculations are correct. Many people prefer marrying off their daughters to Americans & Canadians, i.e., Indian boys living there.