Well, I can see your point, but there are just so many other little things in 3rd edition that don't exist in say C&C, or OD&D - the myriad spells, and things like DR, or counterspelling which can complicate combat.
And not everyone knows all these rules. I'm not a walking rules encyclopedia. To avoid confrontation with my players after the fact, I want to make sure I have the precise rule at the moment in which the event happens. So, rather than guessing that the Resilient Sphere is large enough, I'm probably going to look up how big a Slaad is, and then I might ask the player (whom I expect to know) how big his sphere is. He might have to look that up as well. So, that takes time away from play. And some rules like "can you D-door into an anti-life shell" don't exist in the game, so despite the argument that 3rd edition is rules-heavy, it *still* doesn't cover every situation (and I don't expect it to), but the fact that it tries really hard to do so, leads me to believe that there might be some discussion about it somewhere, so in that situation, I'm inclined to look that one up as well. Those were actual situations that came up in my game, btw. And we had to stop and look all of them up because no one at the table knew off hand what the answer was, and this was a group that had probably been gaming collectively for 50 years or more.