LDO and other regulators cost money, i use them to lower the input voltage,
but why not simply use 2 resistor as you can see here:
That depends...
What do you mean by "input voltage"? If you want to lower the voltage for an input pin a voltage divider is the way to go. But if you want to reduce the voltage of a power supply you will need an active device like a voltage regulator because the load current changes. See the chapter "Loading effect" in the article you linked
As a rule of thumb the current down a voltage divider should be at least 10 times the current you want to take out of the bottom leg. If you have current to burn then go ahead and use a voltage divider. They used to do that in TVs back in the 60s. Nowadays it is just a needless waste of current, and you require large wattage resistors and they are more expensive than a regulator. You need capacitors in both cases.