What's the rationale for this? I have too many quests in my log asking me to do things that I decided my character shouldn't do (kill innocent people, join thieves guild, etc)

You can refuse to take them.

Once you made your promise to collect twenty bear asses to a Jarl though...

The quest system is designed for indecisive people.

You can end some quests though by killing the quest-giver.
E.g.

Well what svcks is having a bunch of quests in your journal and not being able to complete them do to being bugged. Great, huh?!

Because of TOOOOOOODDDDDDD!


But really, it was probably just oversight.

Not if I don't know how they trigger, I can't. There are a LOT of "evil" quests that trigger from not doing anything evil at all.

Spoilers: Just off the top of my head...taking any stone of Berenziah (you don't exactly have to steal one to get it as Brynjolf suggests), talking to one of the first NPCs you come across (gives you the Aventus Arentino -> Kill Grelod questline), reading a book about Boethiah activates a quest that makes you sacrifice an innocent follower...talking to a guy in Markarth makes you wind up doing the bidding of a Daedric prince...that's just a few. There are a TON of "evil" quests opened from everday actions.


Oh, I have these too...damn you, Jarl Skald! This game is a good timewaster, but it's [censored] broken in a lot of aspects.

Yeah, its almost impossible to escape some of the daedra quests. Many of them are very aggressive. You can't even walk down the main streets of Markarth and Solitude without getting accosted and quests triggered. Others just start with random encounters in the wilderness.