1. " I already have 3 social network accounts" 2. "Plus none of my friends are on it" 3. "Plus I don't care if Google succeeds in social." 4. "Plus I keep getting pointless notifications"
I don't really have anything to add to the list since I like G+ But perhaps I can add why your reasons didn't apply to me - if anyone should care. I don't intend to argue - mind you, just offering a compare and contrast, since this is entirely an issue of personal preference.
1) Happened not to be a facebook user - and have a twitter that I don't actually use.
2) A couple of my friends joined but most of em aren't engaging - but actually that's not my chief enjoyment. It's allowed me to discover/follow a whole bunch of really interesting people - and the vibe seems to be that most folk don't mind you following them - and will often follow you back. It's like twitter in that respect - but because it allows longer posts, it allows me to better find interesting posts. Because of twitter truncation and url obfuscation - I could never tell if a link might be worth clicking - and so generally never bothered.
3) I don't care either. But I must admit I wouldn't mind seeing facebook at least humbled a little. I just hope Google's success doesn't give it a super-monopoly.
4) I agree there needs to be improvement in this space. I want to be able to configure my stream to default include only the circles I dig the most. Lots of people have said this though - so I don't doubt that it is in the pipeline.