Why do people feel the need to capitalize things that aren't proper nouns?

I see people do it all the time. They’ll capitalize adjectives and improper nouns for no reason. They’ll do something like this, “So I took my Dog Spot to the Super Market to buy some Dish Soap. When we crossed the Street we saw a little Girl that was playing with her Dolls.”

Some people even do this: “Why The Hell Am I Doing This Idiotic Thing That Undermines The Work Of Centuries Of Hardworking Linguists.”

What is this? Where did this come from? And how do we make it stop? :(