That's true only to some extent: people keep on their keyring only those keys they need for daily use. Less frequently used keys (e.g., keys to a safety deposit box at the bank, keys to a home safe, keys to a second home) are typically stored in a drawer, a closet, or a safe.
Also, note that having different keys means one can give copies of different keys to different persons for different purposes -- e.g., copy of the home key to a baby sitter, copy of the desk key to a co-worker, copy of the home key to trusted neighbors.
People today intrinsically understand that they have to be mindful about whom they lend their keys to, who gets copies of their keys, and where the keys are stored.
Conventional locks are far less secure than most people would realize.
That said, your house isn't directly connected to 2.26 billion people who can make hundreds (or thousands or billions) of bump-key attempts per second.
Also, note that having different keys means one can give copies of different keys to different persons for different purposes -- e.g., copy of the home key to a baby sitter, copy of the desk key to a co-worker, copy of the home key to trusted neighbors.
People today intrinsically understand that they have to be mindful about whom they lend their keys to, who gets copies of their keys, and where the keys are stored.