Actually Duke, there is one important difference in actually naming the mechanic versus printing functional equivalents of it.
(Though, to be technical, equipment would not quite be functionally the same if it were changed to the way you said it. Equipment can switch creatures within the same turn if need be, and if your opponent taps your equipment, it won't prevent you from using it more. But this is all beside the point.)
The real difference is that if a keyword exists, you can reference it.
To use another example, consider how Undergrowth provides the functional equivalent of the Kicker mechanic, without actually being Kicker. The difference is that Undergrowth can't be countered by Ertai's Trickery, nor would you get a token for your Saproling Infestation. That's a very unexciting parallel, I know, but it's a solid outside example.
As to this equipment situation, sure, the eqipment mechanic itself isn't very exciting, but what's to say there won't be cards which won't trigger upon the activation of equipment, or do something when equipment comes into play, or searches your library for target equipment or get +1/+1 for each equipment in play?
Consider morph. (Well, be it known I'm not too fond of morph anyway, but it's another good example). Morph taken entirely alone is very simple and mostly useless. It's what's printed on the morph creature itself that keeps it interesting, (Either surprise combat abilities, or triggered flipping over tricks), or it's the other cards that reference morph that make it interesting, (Runecaster, Weaver of Lies, etc.).
In fact, I think it's safe to say that the success of most mechanics lies not in the mechanic itself, but in how the mechanics are referenced by other cards. Consider how much more interesting echo could have been if there were a creature which drew you a card whenever an echo permanent came into play, or a creature with power and toughness equal to the number of echo permanents in play, or a way to make permanents lose echo, (To avoid paying it), or a way to search for target echo card. There's no "Ixidor" for echo, or for kicker, or for most older mechanics.
Equipment will be what other cards make of it, not what it makes of itself.