Anything that has a practical application in the real world most certainly does has a place in a teaching environment. Calculators can do things most human brains cannot. Professionals from office assistants to scientists use them on a daily basis, and the average person isn’t going to learn advanced functions by tinkering around with an instrument he or she has never touched before. Imagine an employer asking an interviewee whether he or she has experience performing advanced functions on advanced calculators, and the interviewee replies, “No, but I can read a freakin’ manual.”
Students shouldn’t be encouraged to use calculators as a crutch or as an excuse not to master basic arithmetic, but there’s nothing wrong with using calculators as tools in higher-level math.
So, how did the average person learn to use "advanced functions" when calculators were new? Presumably, these people are adults who have already mastered basic math. How many "professionals" have gotten into paying positions without first having learned to use calculating devices? I must have dreamed getting through college physics courses without a calculator. I did learn, however, on my own to use all those advanced functions when I could afford to buy a fancy calculator, after college.
Children should not use calculators until they have mastered the basics. Calculators are a crutch. They can do nothing the human brain can't do, given time and expertise. Pencil and paper are the tools they need, and good instruction.