It all started with wanting your car to look like a Race Car. Ted Horn's out of New Jersey is a good example.
Around 1966 Nascar rules changed a little and aerodynamics improved for free. Maybe not so important at 60 mph, but then again ......
I was born in merced, lived in Modesto and hayward.full dairy ranching portagee..my dad lived there middle 40 's I was told,.. by uncles and my dad... Rake is lowered in the front, dago rake lowered in the rear..and it had nothing to do with San Diego.. my dads 41 ,winfield custom. was lowered in the rear w/ a carson top.... dago was a slang for an ethnic group nationality ... like calling a white guy a cracker.....people lived just fine with "Sticks and stones may break my bones, but words will never hurt me" here's another one.... the carson top..... now if you cut the top off a hard top... it's a cal convertable.....
In my youth the "Hot Rods" were mainly 40s models with a later V-8 swapped into them. They usually were heavier in what they were replacing and resulted in the "rake". So others just lowered their cars to join the charade.