Cory Magel> That's harsh...
Well (and this is NOT direct at anyone on this thread let alone the entire forums), the only reasons I see to change profession are...
A) You're tired of your character.
B) You're seeing diminishing returns and just want to pay less for skills.
Reply to A) Make a new character. (we even let you start a character 1-4 levels [roll a 4 sider] below the one you retire).
Reply to B) Tough.
Now
THAT'S harsh.
Why are you opposed to the changing of professions?
There are a few reasons, but they all come down to this: The player suddenly has the ability to develop a set skills at far lower costs then they previously did.
Why on earth wouldn't I start off as a Fighter, gain enough levels to pump up a couple weapons, my endurance points, etc (basically become a pretty decent fighter) then switch to a pure caster of some type? Anyone who thinks this should be allowed simply
does not understand game mechanic balancing (or just doesn't care, in which case why even have rules?).
You can say it's unbalancing but is this really why? There are unbalancing factors all over the place? Real life isn't fair. Fairness is unrealistic.
As others have mentioned, we don't game to experience the realistic unfairness of life. Cheat at Monopoly with your friends then try to justify it to them by saying life isn't fair. I think that will almost always go over like a lead balloon.
Is it because you really believe in the archtypes? Allowing the change doesn't fit your view of the world?
Well, the destruction of purpose of archtypes is one of the side effects (and one of the few reasons I elude to at the start of my answer in this post), but I believe far less important than simple balance. It has nothing to do with my view of the 'world' because in RM anyone can do anything... they just have to pay for it. By allowing casual profession changes without harsh penalties or controls they
effectively no longer have to 'pay for it'. (Yes, I realize they ARE paying for the skills, but going from paying 25-50 DP for a spell list level to only 3 DP is completely out of whack and would utterly destroy character balance).
One of the other reasons ties into archtype, and is a tabletop philosophical discussion we've had before. We play to have fun as a group of friends. This almost always takes the form of a group of adventures (Players) against the world (GM). This almost always needs to have some level of accomplishment to be fun for most players (and if we don't have a balanced game it's really not very fun for most people). This almost always involves the need for teamwork among players. If you can essentially develop whatever skills you want cheaply and quickly there is a problem with balance among the players unless they ALL do it. If they all do it there is a problem with balance in the game, so you unless you just want them to amass huge amounts of power quickly and steam roll everything in the game you really just end up with an 'arms race' in your campaign.
You also start to see a problem where all the characters can do everything they want (fight, fly, throw firebolts, heal, etc, etc) which undermines the need for teamwork... which is part of the very reason archtypes exist. So, I know it sounds to some like a 'the sky is falling' statement, but even if someone doesn't realize it allowing easy change of profession pretty much destroys the entire idea of why many of us play RPG's. It's one of those things that you have to be able to see the bigger picture to really get your head around. You have to REALLY ask yourself WHY you're playing and then you have to think about how the basic foundation of the game system accomplishes that.
Much of it is intertwined. Archtypes exist to encourage teamwork and to balance the game. Without teamwork and without balance, why are you playing a RPG with a handful of friends around a table? Why not go buy the latest computer game, jump online and immediately find a hack to make your characters all powerful?
Is it because other players would object? If the pc's are more powerful you just chuck a couple of extra monsters at them...
It is because if you only have a limited number of players do it they would become far more power than those who did not, which would lead to everyone doing it, which undermines the entire reason for much of the system mechanics.
So, what is the real reason?
It lets you have everything... and in the end that makes the game boring.