Well i don't know how it works in Norway but this is not only about the age. But here each month there is a bit of your salary that goes into the retirement pension system (which will pay your pension when you will retire) and you have to pay this for at least 43 years to have a full pension. For example, i started working at 25 so i will only be allowed to retire at 68. If i want to retire earlier i won't have my full pension every month. And if the law was just about that i would be fine with it because i started working later so i retire later, it's logic. But if you take someone who started working at 18 will have to leave at 64 meaning you will have to work 46 years instead of 43 with very little benefits because your pension won't be much higher.
Our system is basically what you described, if i remember correct it's about 2.5% of my monthly salary going to the pensions fund, hence why they're also trying to get us to save for our pension ourself, because 25NOK a month (€2.5) isn't much. And when we retire some of us will be low income pensioners, meaning its about €1800/2000 (as of now) we get from the State to live on.
We just don't have the age limit, if someone wants to keep working and can work they'll usually be allowed to do so. We did have something called early-pension but it has been phased out, my aunt (now 66) was of the latest people to be able to get it, but she opted out to be able to work up more and get more out each month when she decided to quit working.
Pension is tricky, and there's probably no right way, and I'm not defending the French government in any way, I know I live in a country where the welfare is higher than most other European countries, and even our systems has flaws, most of our unions suck (and that's why I'm not a member of any of them, really, even if I get some benefits from it
) and I'm just not used to the way of protesting that we saw in the posts, that's all, and as I said: I fully support you all in the right for a democratic process, that's what all of our countries are built upon (thank you for the French revolotion btw, it helped us get out own Constitution
).