GNU grep, the most widespread implementation, does not include egrep, fgrep and rgrep for years. Distributions (not all, but many) provide shell scripts that simply run grep with corresponding option for backward compatibility. You can learn this from official documentation.
Also, my scripts are not full of bashisms, gnuisms, linuxisms and other -isms, I try to keep them portable unless it is really necessary to use some unportable command or syntax.