Soap and shampoo bottles

When taking a shower I have multiple bottles of soap or shampoo that I use for different purposes. Having applied one, my hands are now slippery, yet I have to handle and open further bottles. I am thus inconvenienced by that they all seem to be made in a convex rounded shape with no hint of help for human digits' grip. Conversely, my laundry detergent bottle is of a useful shape that appears to anticipate wielding. I wonder why the bottles that I use in cleaning myself are not more helpfully designed.