I have always been of the opinion that no one is better qualified to determined the shape of the rules than the people actually playing. Rulebooks are great for providing basic structure but not as well suited at being an ultimate authority for everyone who plays the game. The spirit of the rules have always been more important than the letter IMHO and flexibility is the best way to ensure that the letter of the rules remains in tune with the spirit and feel a particular group is looking for.
I disagree here. This is one of those things that sounds great when you say it and a ton of people will chime in and agree with you. However, in practice is had problems.
Strong RAW give you a foundation for your game. Playing RAI means things are murky. It can lead to inconsistent calls, you are guessing at what the writers intended, and the biggest problem it is often leads to on the spot calls.
On the spot calls are really bad. Your options are to delay the whole game while you read through the book and try to figure out what was intended or to make a haphazard call that you can later find out is a huge mistake. Ideally the people writing the rules have more experience with the system than you and there is a reason certain things are set-up certain ways. Later on your off the cuff ruling could combine with other off the cuff rulings and lead to something absurd which you now have to make up another rule on the spot "that is not allowed." It takes too much time to consider all the consequences of a ruling to do so properly during a game.
People also get emotional with RAI. I rarely see people striving for the real RAI. More often that are pushing for the "Rules as I want them to be" or the "Rules as I think they should be." RAW is a more emotionless interpretation, it just needs strong rules to work well. If a rule is written vaguely you are forced to interpret and that interpretation can go wrong. Meanwhile with clearly defined rules you are a clear correct interpretation, even if it is stupid. Using strong RAW if it says you can wear pants on your head for +1 AC, you can wear pants on your head for +1 AC. You just admit that rule is dumb and move on.
That's why I am a fan of strong, well written, and thought out RAW. You can then house rule or do whatever if you want your game to be different. The solid foundation from the RAW will making the game with your house rules better.
The big problem with solid RAW is that they are very hard to do correctly. It really does take iterating, you have small team writing the rules and a huge player base beating on the rules attempting to break them. The larger population will always win. Just look at video games as an example. All the great multiplayer games have gone through multiple iterations. No one gets Starcraft or Street Fighter right on the first attempt. The only games that don't need balance patches are single player games where you don't care about the flaws in balance and design that get found. This is a problem for D&D because iterating to keep up with player innovation is very difficult.
