Those were just examples and they served their purpose; to disprove the fact that you are forced to start every quest in one way or forced to end them in one way. Your examples are just examples of ignoring quests... which also just goes to show that you are not forced to do every quest.
Of course you're not "forced to do every quest" - but the game prompts you excessively and is clearly designed with the expectation you will. And really very few quests are anything other than totally on rails.
Kill them, then they won't keep trying to talk to you. If they just wait around and you don't talk to them, how can you be sure they're waiting there because you went off script?
In many cases the game won't let you kill them without mods. Because it doesn't want to allow you fail quests.
And why else are they rooted to the same spot for all eternity? Why will that Markarth guy wait until the end of time in the shrine of Talos with, if memory serves, no option at any point to say "look mate, I don't care about what you're on about - please just do one and don't be sticking your quest in my journal clogging it up with all the other crap I have to scan through each time I'm trying to look at what I actually want to do." You go and talk to him or choose not to but, again if memory serves, there is simply no option to decline the quest from the outset, which is the case with a lot of quests. I don't recall there being any option with that quest to say "er no sorry, I don't care and won't be investigating this one."
It's just really shoddy writing. Bethesda seem unable to grasp the concept weaving together RPG narratives. Take New Vegas - which they published and tdid the QA for, so they know it intimately.
So one example - you have companions with real characters and stories. So
- You might encounter hidden valley and the BOS and have to do a task to get in with the option of following their questline
- You might enounter Veronica and take her as a companion and might trigger her quest (which isn't at all obvious, you're given no prior indication it exists and have to discover it for yourself and it can be missed) and be asked to go there with the option of doing her quest or ignoring i, which also opens up the BOS questline.
- You might choose to try to change their leadership or you might choose not to.
- Depending on who you support, you might be asked to kill them all, or you can choose to leave them alone or in one instance negotiate a settlement - contingent on whether you chose to change their leadership.
- One faction leads to a selection of quests and options all weaved together into an overall story involving them that can lead to some really tough choices depending on what you've chosen throughout the game. And whatever you do, the game leads you to consider Veronica. Since she's properly fleshed out and has an actual personailty, there's a good chance you're emotionally engaged - unlike Skyrim where everyone is made out of cardboard and all the companions are 2D pack mules you know nothing about (like who's Lydia? What's her story? I'd actually like to know and then I might care about her), with the sole exception of Cicero who is a 'love him or hate him' type tied the DB questline. Why Bethesda can't learn from and build on this far cleverer approach to narrative structure and emotional engagement they've been intimately involved with I really don't know. I'm dreading Fallout 4 because I love that franchise and Skyrim gives me dark forebodings about how badly written it's going to be.