I tried to clean the gutters today.
Failed. Got scared shitless. 
I don`t even see the point of gutters to be honest with you. I have a large overhang on all sides so its not gonna hit the house and splashback and its sloped fine so its not going to collect. Originally it of course didn`t have gutters. It has them now and they route the water underground to a little stream with rocks. Totally pointless though. Fuck I need to clean them though.
I think you're right, if your roof has the right slope you don't need them. Especially if it was designed without them. Same with the lack of soffit vents on old houses. I think they can be very important when you have a lot of roof area that sheds into an area with poor drainage too. That can force water into your basement.
I like those old traditional homes with slates roofs that have the channels built into the roof, where the downspout comes through the overhang. Some are lined with copper and have really great looking copper down spouts. I also like those big old "half round" gutters they used prior to the 60's with the huge round downspouts.
If you've got gutters though, you should probably either keep them clean or take them down. Especially when it's freezing and you can get those big ice dams that destroy your roof.