Just imagine, you start up your own farm. You wake up every morning, go out into the fields and water the crops, hoe the soil, whatever else. Then one day you realise that this is all boring as hell so you decide to go off and do some adventuring. But then you realise that you will need someone to watch the farm and tend to the crops, so you must stay there and keep working for your money. OR you get someone else to do it and pay them less. Now, you don't have to deal with this boring element of gameplay you wanted for some reason, but now, you are getting money for free at a consistent rate. What is your drive to plunder anymore? You're just getting it automatically from your profitable business. Just make some more farms and hire some more workers to increase the flow of income. Are we really playing a 1st person adventure RPG anymore?
I'm not saying turn TES into the Sims. It's simply an added feature for an added variety of game play.
The beauty of TES is that there are so many ways to play. IF you one day wake up and realize it's boring as hell, then you abandon that profession and move on to something else, and the developers could simply design the farm (or other profession) to only be maintained by the player (hence, sidestepping the automatic profit).
Again, the idea of professions doesn't have to solely entail a farm -- that was just an example. I am not proclaiming that millions of lines of code be generated per profession. I would be happy with anything along said idea.
For those who wouldn't want utilize a profession to role play in game, then don't. Many people don't like to play as an Argonian, but others do. Does that mean that because 100% of players don't play that race then it should be removed? No. I would bet that if a profession-style, moneymaking system were to be implemented, the majority of the player would incorporate it into their game.