I think there is no need to include composer for loading any library etc. Loading some libraries is not hard task. Its easy to include...
Download library > extract > put into your project > use it
This task is only one time per project. I mean its not over and over again.
Updating is not huge task too... just download and replace with old files in your project.
this is just 30 seconds for each library. I do not see any reason to include one more layer (composer) to my project.
Plus if we add this layer (composer) to our project, it brings its own problems. Check this to see how many people dealing with composer errors; https://stackoverflow.com/search?q=composer+error
I think I overlook something here. Because almost everybody use composer and recommend.
Could you tell me what I do overlook about composer? What are the benefits of it?
The nice thing about Composer is that handles downloading libraries for you all by itself. All you have to do is specify a list of the libraries you want and Composer does the rest.
These things you think are easy to do manually (updating library versions, including them in your project etc) are all done automatically by Composer. What do you think is easier for yourself and your dev team? Installing a bunch of libraries manually - or installing Composer, writing a single composer.json file and typing "php composer.phar update."
The biggest benefit of Composer is that it will automatically grab all libraries required by the library you want. Suppose you have a library A that needs B, and B needs C, and C needs D etc. Without Composer, you would have to do this yourself. And this takes time and risks error.
Let me know if you have more questions about Composer. It will save you a lot of problems in the long run.