The current you draw from a voltage divider should be small compared to the quiescent current. If you want to draw 1 A from a voltage divider that divides 10 V down to 5 V, then you might want the quiescent current an order of magnitude higher, so 10 A for example. This divider will consist of two 0.5 ohm resistors. Drawing 1 A through these resistors will reduce the voltage to 4.5 V instead of 5 V due to loading (bad load regulation), and in the mean time you will convert 50-60 W to heat in each of the resistors, even when not drawing any power. A linear regulator will be an order of magnitude more efficient under load, and maybe four orders of magnitude when idle, and a buck converter might be two order of magnitude more efficient under load.
For tiny currents, like the base current of a small signal transistor, the current drawn from the divider is negligible, so you can use much larger value resistors. This is where voltage dividers are commonly used.