Crafting was a late addition during the development prior to the initial launch. Like dyeing gear or PvP it was done via a limited budget and the time constraint of must be done by launch time like all the other launch features.
Turbine came up with the node concept for gathered materials. It is done that way because a lot of other games implement resource gathering this way. Swtor which is a much newer game also use the find a node on the landscape and harvest method just like Lotro.
It seems like these reasons were used:
1) Players would be comfortable with this implementation because it is a standard accepted way of doing it.
2) Supply is limited based on the need to have a character high enough to survive in the field. It is time consuming running around looking and gathering materials. It is difficult to automate so that your PC can play your character and gather unlimited quantities while you sleep, do laundry, clean or working. You will find people do full automation for farming.
3) Experience points for crafting are new. It was perhaps 18 - 24 months ago (five years after launch) that Turbine added experience points. I have no idea why. Some people hate it. Other like me love it. The majority probably do not care.
My personal opinion. I suspect there are a lot of people like me. Gathering resources is already very time consuming. Any change that would make it more time consuming is not going to be acceptable. Likewise - special mine concept - forget that. I like being able to do my quests and have a side of material gathering at the same time.
When you get to higher level and higher tiers Turbine has created the concept of a resource instance. There are a lot of ore nodes in the ore instance. There are a number of quests within the resource instance. You get kills for slayer deeds. Barter tokens for various loot. Experience points. Quest completion credit. Along with the ability to get a bunch of ore, wood ...
Unless stated otherwise, all content in this post is My Personal Opinion.