"Without the make install
" is the problem. The include files and built libraries are scattered all over the source tree, as determined by the build system. make install
collects all the headers that are appropriate for use by users of the library and puts them in one directory for including. It does the same with the libraries themselves. make install
may also "strip" the libraries, which drastically reduces the size and improves the load time.
If you don't want the installation in a system directory, you can set the install path to be somewhere in your home directory.