control panel on/off switch

My control panel does not have an on/off switch. When it is plugged in, it is "on". I do have an E-stop circuit which controls a contactor that shuts off power to the entire panel. Is there a downside to putting a simple on/off switch in the E-stop circuit that controls the main contactor? I have seen more elaborate on/off arrangements using a momentary switch but I don't understand why that is necessary. What am I missing?

I put a power switch on my panel so I could include a safe start interlock. Got the idea from Kal. The nice thing is that I can plug the panel in, but to start the system I have to have the elements and pump all turned off. On top of that, because it's a momentary PB I have to physically be standing there, looking at the panel to turn it on. It's just another step to make sure that I don't dry fire the elements and that I'm actually ready to brew. I ended up with an extra momentary PB that I had other plans for but decided not to use, so I included that as a power off button. The off was probably completely unnecessary as I can just as easily use the estop, but I had it so I figured why not?

By using a momentary switch, you will need a holding circuit to keep the circuit energized when button is released. If you lose power you will need to push the start to re-energize the circuit. Useful when you want to control equipment restarts. If you use a simple on/off switch (IE maintained) it will re-energize when power restores.

You also have to physically be at the panel to push or reset the e-stop button. However, due to power outages and other distractions, a momentary push button and related holding circuit would be an added safety feature. If power was to go out for any length of time, you could get distracted and involved in something else when power is restored and forget about your equipment possible causing extensive damage. (unless you remembered to hit the e-stop button) So, you could say that the momentary push button is an auto-off feature to prevent unwanted/untimely restarts.

Thanks! I figured there had to be an advantage or people wouldn't go to the bother of the added complexity.