Force carbing vs. Serving pressure

I have a keezer with 4 kegs. I typically set my regulator to my desired level of carbonation and wait to force carbonate. Then I burp the keg and reduce the pressure to 5-10psi for serving.
Right now I only have 1 regulator. Is there any reason to have more than two? That would give one to force carbonate and one (with multiple lines) to serve from at a constant 5-10psi.
I see some systems with 4-5 regulators; what's the purpose?

Someone with more experience may correct me, because I don't have a multi-regulator setup; that being said, I gather that people put multiple regulators because some styles call for different serving PSIs. That way, they can serve a Cream Ale with higher carbonation than, say, an IPA. And they can also force carb, at the same time. Basically the more regulators, the more freedom you have to serve different styles at different PSI.

The vast majority of us don't use different carb and serving pressures. Lower serving pressure will leave you with flat (or at least flatter) beer by the end of the keg. Knowing that, you can see why some people need to have different pressures available for different beers.

Check out this well illustrated thread for a good write-up

I have three. The primary runs at 35 psi for soda and supplies the secondaries. One secondary is set at 12 psi for most beers and one at 2 psi for "real" ales.