Do people use 3D printers in their careers?

Yes, they do. Working for the automotive industry, we always 3D print parts before asking suppliers for samples. We check fit and sometimes create complete prototypes out of 3D printed parts. Let me take it one step further, I use 3D printing in my personal life as well. The other day created and 3D printed a gauge cluster for my project car to house some aftermarket gauges.

In short, the industry uses 3D printing a lot and people started to use it in their home projects.

Yes, they do. For one thing, 3D printers are advancing everyday into many areas of production and prototyping. 3D printing and CAD allow rapid prototyping, virtual prototyping, fast turnaround, powerful conceptualization of new designs, automatic documentation of every change of a 3D part, and lots of fun.

There are plans to replace the high expense of warehousing and transporting replacement parts that may or may not ever be used with datafiles and 3D printers. There are companies that have already 3D-printed complete aircraft and automobiles and entire buildings. Materials used for 3D printing are evolving so that we'll have not only 3D-printed materials that look like wood and metal, but behave and actually are metal. There are even efforts in producing "scaffolding" for biological structures and printing actual human organs. Food companies have used 3D printers to make snacks and elaborately-designed birthday cakes, among other things.

3D printing is used in medicine to model human organs and bone structures for surgeons to plan their approaches more effectively.

I myself have used a laser scanner to map parts of a patient's body to design perfectly-matched prosthetics and build them with a 3D printer.

So the answer is, "yes". And more probably every day.

Yes.

In their careers and at a personal level. You can buy one right now.