The game of go is said to have simple rules. Simpler, say, than chess, because there is no need to learn how pieces move. However, there are various rulesets (Japanese rules, Chinese rules, differing rulesets such as AGA, ING...) that differ and have some subtle special rules (e.g. "bent four in the corner is dead" in Japanese rules). I think most amateur players would not be able to produce a complete ruleset and you could find game situations where they wouln't know the "correct" application of the ruleset they're using. The rules seem to also have changed a lot in history, usually getting more complicated as far as the subtle special cases go.
The subtleties are mostly irrelevant, since those situations almost never come up. However, I've seen beginners be baffled and disgusted at some of the special rules. The way most go rulesets work, you wouldn't even try to explain all the rules to a beginner (what playing strength do you need to understand how to count seki, let alone "bent four in the corner is dead"?).
However, it didn't used to be like this. A long time ago there used to be a rule that eyes do not count as points (group tax). I really fell in love with this rule recently because it dampens the current tendency towards ever more territorial style of play. (If you want to see some examples of what this looks like, there is a discussion of AI trained on such rules)
Furthermore, these rules allow a very simple formulation. Add superko, then the rules are essentially just "never repeat board position, play until both pass, count the stones on the board to get score". (The old rules had some more stuff we don't use anymore, such as set starting position, but I don't care about that here).
I'm sure the answer is in books on go history but I couldn't find it online:
Why was this counting method changed? Why is it no longer around, while instead several different incompatible ones coexist?
I guess, it might be annoying if you insist to really fill the entire board with stones every game. But surely people didn't do that back in the day? You can resign, or just agree on a score using a different counting method wheen are no subtleties, relegating the official method to have a very simple way of resolving disagreements.
I would love to be able to play this online. Many servers already use "request counting" instead of waiting for both players ro pass. Ease of counting is no longer a concern. A bit more strategic depth would be great.