ADC's splitting/overextending mid and late game. PSA/Rant

When I was climbing out of Silver. One of the constant roadblocks that I encountered was an adc that would try to split push instead of grouping, and would inevitably overextend and die. Depending on the time in game and the circumstances, that happening even once can be a game ender. It happening numerous times is mind boggling. Now that I have one account at Gold 3, and another at Gold 5. I still see this happening from time to time in my games. How is it not fundamental knowledge for an adc not to split push and over extend? Clearing a sidelane is one thing, but farming past mid, as an adc, by yourself, with little to no vision of enemy team? How do people not know better. It's kinda like a Jungler farming a wave on the bottom side of the map when Baron is up, and the enemy team can 100% take it. I just thought I would see less of this than I do in mid Gold. Does this stuff still happen in Plat? when can I expect not to have to deal with that level of ignorance?