Neonchameleon
Legend
This part of your post is very wrong. The mechanics of the AD&D Sleep spell are totally different from a weapon attack, and I do think this is important to why they feel so different in play. First of all, Sleep doesn't have a saving throw; it has a hit dice limit.
I'm pretty sure it does have a save vs spell as well. But this is a minor point.
Secondly, it doesn't do attritive damage. It knocks enemies out, which allows you to easily slay them. It has a very dramatic effect.
And this is precisely what you need. A difference in the fiction. It feels different because it inherently has a dramatic effect. Not because you're making a different person roll the save. Sleep has a dramatic effect because it puts people to sleep.
It's both unified mechanics and the reliance on the battledgrid and minis that results in a less vivid imaginary scene. It's because people don't imagine things unless they need to.
And this is complete rubbish. Plenty of people imagine things they don't need to. I'd argue every single roleplayer does.
Trying to convince people to imagine/narrate things vividly when it's not necessitated by the mechanics in any way and there's no in-game payoff is just lame, passive-aggressive game design, IMO.
Hint: So-called theatre of the mind does not help here. You do not need to imagine or narrate vividly to say "Chop. I hit him for 8 damage". You jsut need to know you are close enough to the enemy and there's nothing in the way. Nothing more than that is actually needed in D&D (and Old Geezer says that's precisely what he did at Gygax's table) - to do more is a stylistic choice with no in-game payoff.
And this throws in that in my experience there are two types of creativity (and don't tell me I'm polarising a continuum). People who create from nothing and then get annoyed when there is something there because it gets in the way of their vision. And people who build and incorporate on what is there and are more than happy to have more things there to build off. Me, I like there to be things there - and find that the battlemat and seeing the relative positioning of everyone to everything helps me build and add detail without getting across everyone else's vision.