Fwiffo: You wrote: "The point is, that two equally strong players should have around the same 'chance' to win. Now, white is already favoured by the rules (60%!!), which is -to say the least- a reason to abolish perpetual raichi."
I would not judge that chance on a single game. The least I would judge it is by a pair of games with swapped colours.
I work with cryptoguru. He is a very strong player with white. He is not so good playing black. He is not alone - he is like many people. Playing white and black are like playing two entirely separate games with separate strategies and even some separate tactics. Playing a successful black strategy takes much more patience than white. It takes more time to master playing black than white for many people because of the attractiveness of forced white wins. This is human nature, it is not a problem with the game itself. Most people here have been playing months not years. When these games were originally played, you'd learn over a lifetime. I think the statistics reflect a lot of learning and hence a lot of bias towards white winning. If you investigated statistics for more mature players and exclude the beginners, I suspect you'd see it even out a lot.
We should allow perpetual raichi because it's part of the game. I don't think it's a goal. It's just an artefact, a side effect. We have no evidence to suggest that it was not a traditional part of the game.