In Finland we reeaaally need ä and ö, nobody would understand ae or oe. So there is need for those
Eventhough such things can be done with software, why not print it on a key if there is a key available that doesn't have a second function?
You obviously haven't been reading the thread. There are more extra and accented characters that are needed by various languages than there are keys on the keyboard. You say "if there is a key available" but there are not enough keys available. Not enough to please everyone, of course. So why should Finland get it's characters, characters that 80%* of the community won't use, before some other country, which again, 80% of the community won't use?
That is the crux of the debate: if you can't support them all (you can't) why support any of them?
One more thing: in order to access the extra or accented characters, you'd need to hit a Fn key combo anyway, so why not just have the AltGr and/or Compose key and solve everyone's problem at once? It's intuitive what keys produce what accented character, so there's no need to print them on the keyboard. Save those Fn key combos for something that is more likely to be used globally, like extra puctuation or currencies.