I have to say in our experience K is NOT "easy" ... From what we got to see during the 1 trimester of K DS5.6 spent at the public school before we pulled him out to homeschool, there are a lot of kids who need remedial services (a lot of our friends' kids are receiving those services). It's not that expectations would be so high ... it's very much like what ultramarina said. What IS hard, is the inconsistent way thing are being taught. The kids spent (rough estimates) 6 weeks working on numbers 0 to 10, 2 weeks on 10 to 20 (if at all?), 1 week on numbers 20 to 30, and the next week they were expected to count to 100 (and this I know only from my friend because at that point we were pulling DS out). DS is a mathy kid so it was no big deal for us (he was bored in math the whole time he was in public school) but it was/is a serious issue from many of our friends. The harder the topics get, the less time is spent on them and if anyone doesn't get the concept right away, there's no time to stop. No flexibility in staying on a particular topic till more kids get it.
Writing was quite demanding for DS who's been always lacking in fine motor skills. He could had used a lot more time just having fun writing basic letters but instead it went from letters, letters, letters to suddenly writing words, labeling pictures, "write a sentence about" ... I doubt very many kids were able to do it but it was very frustrating for me as a parent when I knew my son needed to spend another 2 weeks learning to write the first letter of his name so he'd stop reversing it all the time.
As for reading, I'm still confused about how exactly what they were doing was supposed to work.
So, basically we had a kid who tested well on letter awareness (yet was very frustrated and seemed quite behind in reading skills), who was well ahead in math yet struggling to follow changes in what and how they were doing week to week, and who was lashing out at the OT in therapy for writing because he felt under too much pressure. And because he was the youngest in class, a lot of it was blamed on simple "immaturity".
We pulled him out, gave him ITBS for Kindergartners just to see where he might be at, he got 98 - 99% on all the subtests, he's been working on 1-2nd grade curriculum in Math and reading (now reading easy readers and understanding the concept of reading more every day, and he's our kid who we have been suspecting might have dyslexia, so he has made huge improvements since we started homeschooling), and as for writing, we are doing it little by little. As his motor skills improve, we will be adding more work. We want him to have fun with it.
So, to me, K is not easy. It's hard. Not so much academically as it is emotionally. Those kids who need more academics should have access to it but for the rest of the kids it should be about fun and flexibility and meeting those kids needs. And it's very far from that.
Oh and I should add, this was half day Kinder. So there was pretty much zero time for any kind of play during the school day. It was all push for learning with no breaks and once the kids got home they had to think about homework and projects and other stuff for school. I want my 5 year old to play. He's a kid, he should be allowed to play. And quite frankly, I am not interested in spending hours weekly doing "family projects" for school. I get that it's the schools push for the parents to be involved in their children's lives but we are already involved, a lot and it was taking away time that we wanted to spend doing things we as parents found important.
All I can say is Kindergarten left a very bitter taste in my mouth.