Pet insurance is certainly an option for low-income pet owners, but for whatever reason it hasn't taken hold in the US, where less than 1% of pets are covered. Vets have a somewhat negative impression of it, as it tends to be overly restrictive and, of course, doesn't cover pre-existing conditions.
Crowdfunding healthcare for pets is a fairly popular thing on GoFundMe (50M monthly users, only slightly lower traffic than Kickstarter), Indiegogo, and YouCaring. We think it's a unique and active enough niche to deserve its own, dedicated site, where the funds go directly to vets so as to better avoid scammers who just "claim" their pet is sick.
As with any crowdfunding model, most of our marketing is done by the pet owners (to their friends and family) and the vets providing the care (to their other clientele), so we're not dependent on inspiring strangers to donate.