The market has definitely changed: HP only has 8 calculators on their web site, and the hp50g (the last descendant of the hp48 series - or of the hp28 series if you look even farther back) was discontinued in 2015.
all one needs to do is buy an "graphing calculator" app?
I have and use an hp48 emulator on my phone, but it's not the same as a real 48, so I have two of them kicking around at all times - one mostly at the office, one at home. I have an hp48sx that I bought in college, so it's more than 20 years old, and a 48G I bought off of craigslist about 5 years ago.
Even on a smartphone with a large screen, the interface on a real hp48 is better - the positive feel to button presses and the lack of swiping issues are the two things I find the most beneficial about the real calculator. Just turning it on is easier on the calculator - push the on button, no unlocking, swiping to the right screen, etc.
Even for a simple 4-function calculator, I'd rather use an old hp than a phone. I have a bunch of old calculators and at different times I've used an hp34c or an hp12c - even with LEDs, they last a long time on a set of AAs. (I'd fire up my 28S or 41CV except that N cell batteries are a pain.)