“It’s ridiculous that under current law you can have a video of someone bashing out a car window, but if you can’t prove that the door is locked you may not be able to get an auto burglary conviction"
So what? Surely you can still get a conviction for criminal damage (as it's called in the UK) or theft?
"In California a misdemeanor is defined as a crime for which the maximum sentence is no more than one year in county jail."
A year in jail is a serious punishment. Why can't these people be prosecuted?
At any given time, any given American can likely be prosecuted for a misdemeanor.
The question you are asking is, why are these people prosecuted only after every misdemeanor crime which is prosecuted, and additionally only after those misdemeanor crimes which counterfactually would be prosecuted before this one if more misdemeanor crimes were prosecuted?
The answer is complex.