IMO this gives a much better inherent understanding of equations, rather than just plugging in some numbers into a calculator and reading what comes out.
The value I can imagine with generating graphs on a calculator would be trying a large number of graphs that are too numerous to print in the text book or to organize in some big table of graphs. That's also the value of a scientific calculator which is faster than looking up trig functions in tables, or a basic calculator that's faster than doing arithmetic by hand.
And yes, drawing the graph by yourself is for sure the way better way to learn something. But what do we know ...
There are a number of scientific calculators that actually do a pretty good job at this, and they’re dirt cheap to boot.
Disclaimer: I'm originally from the UK and well versed in "old school" approaches :)