Phil1923 said:Why transform a raster file to a vector file.
There's not only about "resolution". As you said, high quality bitmaps cab be enlarged and maintain good resolution. Think about a poster or wall, sometingh like 2 meters wide and 3 meters height. If you use a vector file (text, gradients, fills, a lot of shapes, etc) the file size will be 10 or 20 Mb. A raster image with this size and high resolution will be a very huge file, that most plotters can't reproduce, and you will need to reduce resolution and quality. With vector files, you can enlarge to 12 meters with almost the same file size, but if you create a bitmap with 12 meters wide, it will be a very big file, although you use less resolution.
But there's a lot of other issues, for example, on a vector file you can overprint fills or outlines easily. For the printing industry, is very important to overpint Black, specially with small texts, for a better print result. Yes, you can do something similar with bitmaps, but it require more job, and with vector files is automatic. Another important thing is the trapping, to overlap one color to other. That is not possible with raster images, and it's also very important for printing companies. Overprint outlines is also useful for exact match shapes.
Sometimes we need more than 4 CMYK colors, for example a Pantone color. Why? You can create a full color cover + Gold or Silver. Or, you can use a Spot color for create an UV varnish. It's also required for cutouts and for send to cut on a plotter. But maybe the job only use one color, or two colors such as Orange and Blue. Most corporate logos use one or two spot colors, and it doesn't allows to use a different color. So, if you want to create a brochure, envelope, business card, magazine, etc the best way is to use vector files.
On the other hand, raster files are more realistic, and sometimes is needed to add a real image