I think the point was that they wanted to distinguish the Warlock monster variants so they're not all just blasting Eldritch Blast every round but instead are interesting and distinct from each other. They wanted to make it easier for the DM to pick the most interesting option and not the default "the warlock blasts you again."I don't find a Xd10 force attack at 120 ft range to be complicated. Certainly, it's not for wizard analogs. Add it to the actions list and be done.