No doubt, that it is good to have these (what we here called) type classes.
But the way it is implementation in SD has some disadvantages, as I see it.

The user defined classes are always connected to the type classes (selector is “class.class”).
Because of that it:
1. causes redundancy in the CSS.
A class must be defined several times, when it is needed for different types of elements. In the example I added in this response you see that the class “margin2” is defined three times with the same values for the elements ‘container’, ‘link container’ and ‘text link’. You can not define the class ones and then use it on different types of elements.
2. can cause human errors.
On different types of elements, a class with the same name can define different styles. In the examples you see that the three instances of the class “my-color” all have different values.

If there would no dependency between the type classes and the classes the SD-User creates himself, he/she could define a class one time and use it everywhere.
(I attached only a screenshot, since I could not add a rsd-file here)

need to press this in suggestions topic.
I think its awful, and since the very first release, one can not set a default font, deafult text decoration, background, or even borders. Once has to create a custom css file, and update it separately, or update every single different element everythign a site-wide change is made - and symbols do not support this.

So what is "apply to elements of this type" if not setting defaults? Colours backgrounds styles

Actually, for me, part of the excitement, the reason for being alive is not actually setting defaults when a new project is conceived and evolves, but letting the design juices flow as the project evolves. I call it living a little, something I sometimes suggest to others..

If however there is a need for setting default fonts, sizes decorations background colours, you name it and do the same for any other element that you care to mention, then that is done as a first thing, by creating a blank page I re-name that page " (project-name)-styles" this is the page that I add elements and "apply styles" = To all elements of this type, this is often done in collaboration with the client who is the one that decides on such things, except if I suggest them to
" LIVE A LITTLE" , even halfway through any development if one desires to change a font type, for example, one simply goes to the style sheet selects the font and changes the font type, really a quite simple procedure.

Now call me finicky, stupid, or anything else if it makes you feel better, but is that not SETTING A DEFAULT style for all elements within a project?? if that's something you wish to do.