It has to do with the word coming from French to English. There isn't a b sound in the French word. Sometimes, the weird spellings harken back to French loan words.
My guess is that English speakers spoke it with an accent and it eventually morphed into the modern English pronunciation
DC can be transmitted longer distances than AC generally. The problem is that it requires more effort to change voltage levels for DC than simply using AC transformers. DC transmission tends to convert AC to DC on one side and then invert back to AC on the other. Then, all the voltage changes are handled in AC