said by whataname :
I know for Centurylink/Qwest there was/is a $5 or $10 discount for bundling, depending on what and how much you have bundled. So at least that way there is a discount for having the VZW combined.
The other advantages are having only one bill instead of two, and having one company to call if you need to make arrangements. Disadvantage is you can't let one service get suspended and catch up on others.
Not much of advantage today with online bill pay offered by banks and companies themselves. $5 dollars a month is nothing and not worth switching to unified bill. $10 is a more reasonable reason.