The issue of "one seat ride" to Penn Station as the case is, is a little more complicated than the simple minded analysis, or lack thereof that I have observed here regarding choice of commuters.
First of all the hypothesis that everyone has a deep desire to arrive at Penn Station and then get on a subway is clearly a myth, since the World Trade Center crowd usually abandons their one seat ride in Newark or Hoboken and hops on a PATH train (or a ferry from Hoboken) as a choice instead of staying on to get to Penn Station and then get a subway. So we can just discount that as not important. What is important is being able to get where one needs to go most efficiently.
A very small proportion of commuters arriving at NYP work within walking distance of NYP. So the rest get on subway or bus to get to wherever they need to go. I.e. they really dont have a one seat ride to where they want to go anyway. A large proportion go to the area north of Grand Central. This is the reason that the MIS done in the early 90s after a lot of surveying etc. chose Alternative G which would have some trains run through Penn Station, possibly even without stopping there through bypass tunnels and then proceed to a station in the vicinity of Grand Central.
Of course such would require funding a huge project in Manhattan upending lot of people's lives for many years, from somewhere other than New York. For parochial reasons amply exhibited in their postings here by some, that is unlikely to come to pass.
So then the question of getting people to GCT north still remains and Gateway does not address it at all, indeed it makes the situation worse by dumping another 20 trains worth of passengers per hour at Penn Station with absolutely zero additional capacity added to the subway system to disperse them to anywhere. Of course if all the 20 trains worth of new arrivals were going to the Gateway development, that would cease to be a problem, but no one believes that to be the case based on current projections.
The primary goal for a signification plurality of NJ Commuters has been to get to the upper east side, and even onto Queens. Currently they do so by taking E or F trains from the vicinity of NYP. As mentioned before there is no plan to significantly enhance this service. Foreseeing this problem the original Gateway plan had envisaged a 7 extension under 30th St to a station in the vicinity of NYP. That is pretty much not happening since the tail tracks now stretch down to 20th St.
That is why in NJ, based on feedback from NJ commuters of today, as opposed to from the last century, various schemes are being considered for getting people off the mainline trains, which go to the wrong part of New York, somewhere in NJ, and getting them onto an acceptable length of time journey to the upper east side by other means. And that is where 7 to Secaucus comes in.
Now I know there is a lot of invested emotion in a pair of tunnels to New York Penn Station, and I also think that that will be the first thing to happen. Indeed that is what at least one advocacy group that I am associated with (NJ-ARP) is not at all opposed to and it supports Gateway completely and is working closely with the Gateway team on this. Indeed it is at NJ-ARP's goading that NARP came out in full support of Gateway in the recent past. There are other rail advocacy groups who are much more openly hostile to the current Gateway plans.
But the same advocacy group (NJ-ARP) is also considering possibilities to address the ultimate goal of getting easily to upper east side while avoiding the utter mess and chaos that Penn Station is and is going to continue to be. No amount of lipstick on that pig that can be realistically applied will address the real problem, which is dispersal of the hoards once they arrive there. Hence the support for 7 to Secaucus and also for possible future extension from Penn Station to a station in the vicinity of GCT, with a general feeling that the subway option is more realistic and achievable.
The subway option is believed to be more achievable at least at present, because it is potentially cheaper* to build and operate, with fewer internecine problems to deal with. The new construction is almost entirely in NJ so it will be easier to fund and manage the construction, and real estate costs will be next to nothing. It clearly will be NJ's responsibility to build and fund operations of it.
Basically Gateway does not add any additional choices and actually makes the currently available choices arguably worse by increasing overcrowding at Penn Station. It just provides more of the same. So even after Gateway is built there will be need to provide alternatives. Gateway will just create a bigger chaos at Penn Station. It's primary purpose is to serve Regional Rail and that is a good thing that all should support. But it does not address the basic identified needs of NJ commuters, notwithstanding what one person with a last century experience of commuting when many fewer people actually used the system than what is projected to do, might think.
And of course the commuter rail option that was lacking back then continues as such, since not much will change as far as that goes, with Gateway.
* Cheaper to build because subway tunnels do not have to be the larger diameter mainline sized tunnels, and they can take much higher grades and degrees of curvature. Subways are cheaper to operate because of the less severe staffing requirements. The highest component of operations cost typically is labor for on board staff. And fortuitously, 7 happens to go to exactly the right places, and ironically, it even serves the Gateway development better than Penn Station does.
