The real reason why <s>the Fellowship</s> the Company couldn't fly on Eagles to Mordor is because the Eagles are kind of dicks and they don't really care about humans or elves or dwarves or hobbits. Like, the Eagles just watched idly while the elven city of Gondolin got invaded and razed by Morgoth. They didn't even help Tuor and Idris escape!
In Idaho i84 is a glorious 80 mph. Hit Oregon and it's 65, which feels like walking in frozen molasses. Same road, same conditions. It's strange that the rules from the container state object can override the rules intrinsic to the road object, that is what is a safe speed given road and weather conditions