Currently I have all of my deployment scripts in shell, which installs about 10 programs and configures them. The way I see it shell is a fantastic tool for this:

Modular: Only one program per script, this way I can spread the programs across different servers

Simple: Shell scripts are extremely simple and don't need any other software installed

One-click: I only have to run the shell script once and everything is setup

Agnostic: Most programmers can figure out shell, and don't need to know how to use a specific program.

Versioning: Since my code is on github a simple git pull and restart all of supervisor will run my latest code.

My question is, with all of these advantages, why is it people are constantly telling me to use a tool such as ansible or chef, and not to use shell.