So let's say Jimmy is growing up, decides he wants to be a tyrant evil who rule over the world, how can he do that
he can't be a dk, there is zero guarantee if he goes to LK he will kill him and raise him as DK, in fact he will most likely turn him to a simple ghoul
his only option to achieve evil goals is to be a warlock, learn fel magic, done, that simple start
Hence why warlocks are evil
And Meryl Felstorm is a mage, not warlock, try again