In this spam sent out by the California DMV (with the subject line “REAL ID: a must-have for travel in the US!”) in an obvious attempt to generate more revenue, you are misled into believing a REAL ID is mandatory for travel. It is not.
According to the TSA, REAL ID is not required. Check this link for a list of acceptable forms of ID that TSA accepts.
If you have a passport or passport card, you are good. There are lots of other acceptable options that do not require you to pay for a REAL ID.
Shame on the California DMV for this misleading advertising.