The rationale is simple and pragmatic: employers want to find the gold nuggets, but snowflake resumes scream lack of experience and can easily be filtered out in early stages of the funnel.
Inexperienced people often make these intricate resumes w/ fancy templates, but all that tells me is they're fluffing it up to compensate for lack of content - sometimes in a quest for beauty, they don't even spell out their contact information!
My advice to those people is to go talk to a recruiting agency or a local job board. They can help find and correct all of those faux-pas, catered to the local market expectations.