I guess you a are wondering why so many books are produced with InDesign and much less with LaTeX, because LaTeX obviously is suited to typeset the books you are buying.
LaTeX had in the past and has some serious shortcomings yet. In the past it really was a headache to adapt and use a random font. Before XeTeX and LuaTeX had been developed, you needed to rename them in a standard way, produce some kinds of helper files and a *.sty file. If you are interested, have a look into the fonts directory of you TeX-Installation.
But publishers and booksellers use a plethora of fonts. In the late 90' I got a Corel Draw CD containing the software as well as about 600 fonts. Many of the were of high quality, but maybe 15 usable out of the box with LaTeX.
To typeset fancy pages, magazines and books love colors and columns, especially columns running around little pictures or some kind of text inlays. Section design is difficult with LaTeX. And so on. In short: LaTeX isn't meant for graphic design.
You can produce beautiful book with LaTeX, of course! Recently, I have asked for examples of beautiful typeset manuals, see here: Big list of beautifully typeset package documentations . Well, because these days people give their answers in the comments section, I haven't got one answer, but some answers in the comments.