Why do I need my router and switch in a rack?

Most POS companies recommend that some type of cable management be used.

Most POS companies recommend that some type of organized system be used. Having your devices in a rack makes the setup quick and easy.  It also is easier to troubleshoot your POS system.  If your IT area looks like this, then setup will take 3 to 4 times longer than an organized IT area, even if you can find all the drops.

Rack Towers are good, but data ports need to be labeled and identified at the patch panel and at the device end.

If you have an tower with your existing equipment installed on it, then these data ports need to be labeled and organized to be able to identify the other end of the data port.  If these data ports are not labeled, it can take up to an hour, if not more, to located the other end of the data port.  Also you do not know if the other data port is damaged or has a switch connected to the data wire and splitting the data to other locations that can cause problems for your POS system.
If the wires test good, and are easily identifiable, then the existing wire can be used. But it does not guaranty there is not a problem some place else.
These are both useable racks for the POS system setup.

This is not good cable management

These are racks that may be difficult to work with and take time to located the other end.
These are racks that may be difficult to work with and take time to located the other end.

With an IT rack cable management  is much easier

The best installation is to use a wall mounted IT rack. That way you only have one cable being connected to the router from the ISP (Internet Service Provider).  The router is where your POS network starts.  The router connects to the switch which splits the network data and sends it to the individual devices. On the left hand side you can see lights, those lights tell you which devices are connected.  

The rack makes cable management easier. Devices in the rack. Punch Panel, Switch, Router, and Power Strip.
Cable management is more difficult without the rack. Devices in the rack. Punch Panel, Switch, Router, and Power Strip. Without the rack the devices can be knocked off and the system go down.

This is the same devices as the above picture, but without the cables

What the above devices looks like without cables.

Cable Management

For new construction or remodeling, have your GC put plywood up in your IT area.