Agreed. But let me share with you a brief paraphrase of the Amtrak response to my letter of complaint about the situation. Amtrak's position was that most people on the NEC were business travelers, who didn't need checked baggage. Hilarious, even 25 years ago.
Lets think of it this way. Look at the time it takes 67/66 to traverse from Boston to DC or the reverse, even without the crazy layover in NY. Is it worth adding baggage cars to more Regionals, and doubling or tripling the time the train needs to spend in PVD, NHV, PHL, or BAL, just to name a few stations, in order to be able to load/offload the baggage?
67 is scheduled to take 31 minutes longer traveling BOS-NYP than 173, the Regional with the shortest scheduled travel time. And it still takes 26 minutes more longer than 137, the Regional with the second longest travel time. South of NY? Quickest Regional is 93 (HA!) with 3:13, while 67 is again the slowest with 3:58.
Granted there is even more padding in the schedule aside from the long layover at NYP, but you get the idea. In my opinion, the ability to check bags on 67/66 regardless of the service being traveled on simply needs to be advertised better. But, that is a discussion for another thread.