It would make sense for Warlocks to not have ritual casting as a default class feature. Wizards (and now presumably clerics) are learned spell casters, and rituals are magic that must be learned. Warlocks on the other hand have no penchant for learning magic. Their magic is innate and comes to them through their ties to demons or feys.
Things like summoning evil tentacle gods could be done just as easily by making it a daily power.
Things like summoning evil tentacle gods could be done just as easily by making it a daily power.