Every single command, option and argument in the shell is split by spaces, regardless of what it contains. That is clearly the more common case. I am not talking about splitting when the space comes out of a variable but in general, as part of the syntax.
I am well aware of how quoting works to avoid accidental splitting and it is an absolute non-issue in practice once you get used to quoting things, about as annoying as the fact that you have to quote strings in every other programming language, i.e. not at all.