You are getting a very good approximation of DC because you have a very large capacitor and a large resistor. What you are seeing is (probably) just garbage picked up from other circuits (and/or the scope itself.)
This is your circuit:
simulate this circuit – Schematic created using CircuitLab
Here's what the output looks like:
Within a fraction of a second, it reaches a steady state DC that is very clean (no ripple.)
Now here's your circuit with a much heavier load:
simulate this circuit
Here's the output:
There's the ripple you expected.
The capacitor is there to reduce the ripple. Depending on the size of the capacitor and the current drawn by the load, there will be more (or less) ripple.
The Wikipedia page on "Ripple" goes into some detail about the mathematics.
You need to adjust the scope to show DC rather than AC. Set it for something like 2 volts per division. Also, use a slower sweep time. Something like about 20 milliseconds per division. Your current settings are showing you just the noise on top of the DC, and "zoomed" in to see extremely fast "noise" that really isn't part of your task.