It never attracted a giant user base. I miss Reader (especially the pre-G+ integration version) and I wish it was still around, but it's not mysterious why it got killed. If it had hundreds of millions of users it wouldn't have died.
This: Google's scale of operation doesn't work well for a free service with a small number of users - the legal, localization and support overhead is disproportionately expensive on a very small service, unless it's a paid one.
It apparently had only 10k users. 10k users that loved it, but still not really enough for google to allocate resources to support and develop it.
That's astonishing. Do you have a reference for that number?
No - it was a number being thrown around here on HN when Reader got the chop.
The G+ juggernaut rolled over it. Same reason photos went to hell for a few years until G bought a few startups and started over.