D&D 5E (2014) Death strike is grisly

[Uchawi]

That way madness lies. Why can't a Barb rage every moment of every day? Why does a level 1 clerics god answer their prayers only 2 times a day? Why can't a wizard just study harder and memorize more spells? How come a bard can only inspire people a certain number of times?

Because this is a Role Playing GAME. If you just want to make up a story that makes perfect sense to you, you need to give up any premise that you are playing a game with built in resource management and write a story.

It does not need to lead down the path of madness, you just account for more frequent use of any ability that is a more natural fit to the human condition. Plenty of RPGs have accomplished that goal, but D&D and the vancian system places some pretty tight constraints on what is allowed or even simulating what is realistic.