Apple never developed a calculator app for iPads that Steve Jobs liked or was satisfied with.
Jobs wanted the calculator to be a special item on iPads and some reason the software design team just never came through on this.
So, Apple never released a calculator for iOS for iPads.
I believe if Mr. Jobs was still alive, we would have had an iPad calculator by now.
Apple has been promising this for years, since, but has never come through with this promise in seven years!
The iPad calculator app doesn't seem to be a very big priority for them any longer.
There are plenty of third party calculators that look great on an iPad.
Some are free with or without ads.
There is no weather or stock app on the iPad, either you know.
Plenty of great third party weather and stock apps out there that take advantage of iPad's larger screen.
Again, some free with or without ads.
If having no stock iPad calculator app is a BIG dealbreaker for you, you can return your iPad and get a Google Android or Microsoft Surface tablet, instead.
This is a very old observation and I think that since there are so many great third party calculator apps for iPad, over the past seven years, that Apple has just decided to NOT include a calculator for iPads on iOS, any longer.
It is what it is.
This is a very old conversation that doesn't change the facts.
Good Luck to You!