Why I can butcher, pick flowers etc where I want, but not fish where I want?
Not really sure what you're saying here.
You can't pick flowers where you want; only where foraging nodes were programmed to shard.
You can't butcher where you want; only near skinnable mobs.
You CAN actually fish in any water you want, but if you want better stuff, you need to find schools of fish and/or use lures.
I mean need 90 skill to fish in scarwood reach, but to butcher I can butcher any animal.
Ok, that's a good question that I don't have an answer to.
Note that during Summerfest you can fish at any Summer Sunplant at any skill level