In addition to the already-raised issue of subprocesses not inheriting aliases, I'd also be worried about aliases inherently being specific to particular shells. I'd hate to have to redefine those aliases for sh, csh, zsh, fish, and Lord knows what else. It'd also be an issue for invoking those tools without going through a shell in the first place - as is common for programs launching external programs as subprocesses.

That's indeed why I personally don't use shell aliases at all, instead opting for actual shell scripts in my $PATH. Those will work no matter what shell I'm using (if any).