I wonder whether breed rescues have an easier time finding fosters to volunteer for them than shelters do. I could imagine they might, because of emotional attachments people have to breeds that look like dogs they remember from childhood or that they've had positive experiences with or whatever.
chihuahuas and pitbulls are wonderful, wildly underrated dogs.
I used to think I didn't like chihuahuas until I adopted an elderly chihuahua, and she proved to be an angel. I frankly didn't understand the appeal of lapdogs at all, until I found a creature in my care who wanted very little beyond basic human company, and who was so agreeable and sweet that I could take her absolutely anywhere.
Since she died this year, I adopted a chihuahua mix puppy and it has well and truly convinced me that if you do a good job of proving to the critter that the world is safe for them, chihuahuas are lovely, polite, outgoing dogs.
And as it happens, one of his favorite playmates in the whole world is an enormous pitbull mix, who is always delighted to meet him and impressively tolerant of his puppyish nonsense.
I get seeking a breed that looks like the dogs you grew up with, or which you can trust to be reliable around your kids or whatever. But chihuahuas and pitbulls can be seriously delightful and easy dogs to have in your home, and I wish more people would give them a chance.
As for your comment about shelters: you're just plain wrong about that. There's a stereotype that they're about as diligent as the DMV. Wrong. Considering the breed rescue people are mostly unpaid volunteers who don't stick with it very long, it's probably a wash.