Basically, organizations adapt to take as much of your available money as they can at every stage of your life.
In the natural world, food doesn't go uneaten for very long. Cellulose is hard to digest and for a very long time, nothing ate it. Plants just died and sank into the earth and became coal. Over time, critters adapeted to eat cellulose. Why? Because food doesn't go uneaten.
Now consider that money is food. Given a median household income there will be no point in your life where one expense ends without another beginning. Do I have proof of this yet? No...it's just a hypothesis...
...of course some of this comes from us personally, where we have excess money all of a sudden and we think of ways to spend it. But Some degree of that has to be external too...an insurance company knows when a demographic is suddenly free from other expenses and they increase premiums at that age, for example.