Canine / felines are carnivores (omnivores these days, but you get the gist) and their muscle structure / diets cause them to taste 'off' and be tough fleshwise. Not to mention that they're worth more as biological weapons / companions.

There are also more scientific reasons, for example:

There was a quick deterioration in the men's physical condition during this journey. Both men suffered dizziness; nausea; abdominal pain; irrationality; mucosal fissuring; skin, hair, and nail loss; and the yellowing of eyes and skin. Later Mawson noticed a dramatic change in his travelling companion. Mertz seemed to lose the will to move and wished only to remain in his sleeping bag. He began to deteriorate rapidly with diarrhoea and madness. On one occasion Mertz refused to believe he was suffering from frostbite and bit off the tip of his own little finger. This was soon followed by violent raging—Mawson had to sit on his companion's chest and hold down his arms to prevent him from damaging their tent. Mertz suffered further seizures before falling into a coma and dying on 8 January 1913.[8]

It was unknown at the time that Husky liver contains extremely high levels of vitamin A. It was also not known that such levels of vitamin A could cause liver damage to humans.[9] With six dogs between them (with a liver on average weighing 1 kg), it is thought that the pair ingested enough liver to bring on a condition known as Hypervitaminosis A. However, Mertz may have suffered more because he found the tough muscle tissue difficult to eat and therefore ate more of the liver than Mawson

https://en.wikipedia.org/wiki/Douglas_Mawson#Australasian_An...

It is highly likely that if those explorers had asked the original breeders of said animals, they'd have been told strongly that eating them was a bad idea.

http://www.missfoodwise.com/2013/03/beef-stout-and-oyster-pi...

Deciding something is delicious or not has more to do with culture and upbringing than actual taste.