Am I just rusty or is this a problem?

Granted, there is a world of difference between the 70s and 2020s when it comes to brakes and their performance, however, it is most unusual for the master cylinder to be that low on fluid that air gets in the system.
As mentioned above, check all wheels for leaks, plus all lines and hoses, but also I would be checking for worn out pads/shoes, and oversized drums/undersized rotors if you have front disk brakes. You didn't mention if it has drums or disk, but I assume that it is probably disk.
You also didn't mention whether it was power or manual, but it shouldn't be that easy to lock them up IMHO.