Maybe it's because Whatcom County just didn't have the ability to support much advertising on a TV station. Bellingham didn't historically have a large population, and KVOS would have been competing with the big three Seattle stations, as well as CHEK, CHAN, and CBUT. I know the big three made it OTA to N Snohomish County, I'm sure with a decent antenna (or cable) they also made it to the Bellingham market as well.