just think of rooting as granting you admin rights on a PC.. because that's exactly what it is. without rooting you don't have the needed permissions to change the ROM. yes, Fresh and Damage and all the other Devs are incredible at making ROMs, but in order for anyone to put them on their phone, they have to have admin permissions.
imagine if you had a PC that was locked down you you could only add certain apps, you could only change certain backgrounds, and your HAD to have apps on there that you don't want and will never use, but you couldn't get rid of them. Then someone said "pssst... I know how to get rid of those apps and let you change anything on the PC that you want.. but ya gotta do this first"
I work in the IT industry.. I have seen sooooooooooo many of our clients that lock down the PC's for their users so hard that they don't even have a start button available. All of those guys would love it if I told them how to gain access as an admin (it's not that hard)