What concerns me with some of the posts is that some seem to take the responses on why people might not model in O 2 rail as an attack on it, or that it isn't valid or something. Some of the posts came off to me as 'well, if 2 rail O doesn't have a lot of out of the box stuff, if people use that as an excuse not to get into it, they are obviously people lacking skills and patience", when maybe it is they don't have the time to build switches or scratchbuild engines or repaint them or kitbash another style to get the one they want. With HO there is so much offered pretty much RTR that unless you are dealing with relatively obscure prototype stuff, there is likely to be something out there. You can build a pretty nice layout and do it with out of the box, and for someone with limited time, that can be a lifesaver. I realize the original post was talking bigger layout spaces, but the same thing applies, even assuming you use let's say a lot less switches in O, if you do as someone suggested, hand build them, it takes time to do that....I also will add that in the world of 2 rail O scale, many if not most of the people you see in the hobby are older, either near retirement or in retirement, and they have the time. N and HO have a much younger demographic, and knowing younger folks into those scales, they tend to use a lot of RTR equipment and track, pre built structures, between the demands of long work hours (now quite common, sadly), kids with everything they do, work around the house, it is what they can do and have a layout at all..and what I have seen (which is just that, my experience), once they get past the age where they have young kids, when their careers are established, and so forth, then they tend to get more into doing things, scratchbuilding, etc..and they will stay with HO because that is what they know (or N, obviously).
I think there is a point to be made that these days that may be less of an argument, with MTH for example building convertible engines that can go from 3 rail to 2 rail scale, with Atlas making 2 rail O equipment and track, and with the other smaller firms out there making scale stuff, there are a lot more choices than there once were.
And to be honest, it is unlikely that there will be enough people in 2 rail O ever to make it much more than that. MTH is building convertible engines because quite frankly the engineering involved isn't all that great, and their business model is around leveraging technology to get a number of markets (for example, they determinedly went to make their DCS boards as small as possible, and also integrated DCC into them, so they could get into HO scale offerings, something for example Lionel didn't bother doing), they build european prototypes because they design the chasis to be easily re-usable across the product line, and so forth. Atlas has made 2 rail O for a long time, and went the other way with 3 rail.
The real reason O will be limited? Because most people, outside the fortunate few, have space to build a layout that would appeal to them given the sizes required for O 2 rail scale. What runs on 36" diameter 3 rail (or 18" radius HO scale) takes 36" radius curves in O 2 rail scale, and in a given space that can limit an O 2 rail layout compared to what you could do in HO. HO can give you more layout for a given space, and for many people choosing between let's say an HO layout where they can run passenger equipment, versus 2 rail O where they would be limited to smaller engines and rolling stock and not running passenger service, they will choose HO. Also, there is a self fulfilling element here, 2 rail O is limited in part because people don't know about it, yet the market is so small that no one makes the effort to broaden offerings and promote it.
After all, all you have to do is look at the magazine that supports this site, when I started reading the occassional issue of this magazine, it was dedicated pretty much to scale O, with a smattering of 3 rail, and it evolved into being about mostly 3 rail because that is where the numbers are, enough to help keep the magazine going.
If I had the space, I would be torn, because 2 rail for me does hold a lot of charm, as much as I admittedly love three rail (for a variety of reasons, including liking to be reminded of 'playing with trains', I like both trying to make things look realistic and at the same time, something I am playing with). One of the biggest advantages for 2 rail O, thanks to the popularity of HO, is that DCC is an open standard, which means that if a DCC board ever goes south, I have a lot of options (and is easy to replace, thanks to the NMRA connector standard), and if down the line it blows out, DCC is backwardly compatible so a newer generation board will still support existing functions, something you cannot say in 3 rail for example.I have seen some beautiful 2 rail layouts, and I wish I had the time and space to build something like that, but I don't at this stage of life.