Considering Enterprise was retroactively made the name of Earth's first Starship it would actually made sense if it was made a tradition to try and keep a ship of that name in service at all times (with maybe the same courtesy being extended to the other ships in the NX class?), or at least as much as realistically possible allowing for outside factors where unexpected destructions crossover with not having any sufficiently prestigious ships worthy of the name ready to go from the shipyard.
Indeed, assuming the constitution class was the first to follow this tradition, the gap between C and D is the only one really long enough to not follow the idea of naming a new Enterprise as soon as possible after a previous one goes out of service. And that could easily be explained by it being a tradition that waned for a while before some Admiral decided to bring it back.
I should say, I have no idea how that idea fits with either the wider canon or real military practice (though as always with Trek, it has the get out of "It's the future! We don't do thing exactly the same" which gets used for things like the reused registration number for the various Enterprises...) but I like it and it works for me.