Well, yes they do, only it's different with and without CTRL. For example in a text editor (or a normal webpage without any fancy JS):
- Shift+End goes to the end of the line
- CTRL+Shift+End goes to the end of the document
and the same is true for Home (substitute "end" with "beginning").
I have seen people, even "technical" people, select a text with the mouse from the middle of a large Word document to the end, because they didn't know this.
They also had to do it often (several times a day) and it had become a significant part of their workload...
CTRL+A selects all
CTRL+Shift+End selects all from where you are to the end
CTRL+Shift+Home selects all from where you are to the top
One of the (many) problems of web UIs is they often ignore the keyboard completely.