I have an old HP 15C RPN scientific calculator.

- I know where the buttons are without looking.

- It has functions my Android calculator does not have (directly or that I know of).

- It has a strange satisfying tactile feedback.

- It never interrupts me. Ever.

- It never distracts me. Ever.

I reach for it frequently.

I've never owner any other piece of technology with buttons this good.

It is really a lost art.