I would have assumed that cheap (i.e. 4-function, LCD) calculators today have the same internals as cheap calculators from the 1980s. Why reinvent what works, when you can just keep selling it.
There were non-cheap calculators in the 1980s, too, that did proper evaluation. The ones I remember had keys for parentheses, though, allowing you to enter, for example
(3 + 4) * 7 =
For an example see the TI-25 at http://www.datamath.org/Sci/Slimline/TI-25.htm
Rotation changing how the calendar handled order of operations seems even less intuitive to me.
i'd assume that because the ui for the ios calculator app is the same as the ui of a cheap calculator. not sure i would ever consider the platform that app is running on.
Rotate it and the app was a basic scientific calculator.