Standards in every industry and business are important. Imagine that we buy a monitor and its input does not match our video card, even though it has the same type. That's why certain standards apply.
In polygraphy and graphics, such standards also exist - appropriate definitions of CMYK colors - key for the appropriate color reproduction. Specified in advance formats for printing leaflets and business cards, so that they are comfortable and as uniform as possible. Without standards, even leaflets could be completely unreadable and even repulsive.
Printing is not one thing
Printing is not only printing leaflets, business cards or large banners - it also prints other, necessary materials such as: stickers, self-adhesive letters or labels. In principle, everything that comes out of the printing house can be included in the category of printing.
There are plants specializing in the production of only a specific group of printed materials: eg leaflets, or only large-format printing. However, this results from a simple thing: for every type of printing you need to have the right machine, and these take up space and cost a lot. That is why printing plants limit the amount of services provided.
And you also print?
The printing era has been pretty good since Gutenberg. First, important things were printed like books. But these are REALLY important, not some literature for the mob. Well, because the mob was quite illiterate at the time. Then also such fiction was printed, meaning for the reading of the book. Well, since the last 50 years (even hundreds of them), it's all about printing - books, leaflets, business cards, even shirts, mugs, pens ... Well, really everything. Because you need to build brand awareness at the customer, i.e. printing and marketing is an inseparable couple. Because you can print everything on your T-shirt and have it originally. Well, who would prohibit the rich?