As you pointed out, the rush for all destinations you mention is only during the rush/holiday season. For HBJ-LTT or HBJ-NZM overnighter, even during season, you can get a confirmed/RAC ticket a day before.
Like you rightly identified, BPL already has enough passing through trains to cater all year needs, just like NGP. About dedicated trains, they could be weeklies, at most. For seasonal travel, special trains are always run, but the news doesn't always reach the travelers who mostly don't follow print news. Therefore huge waitlists and wails.
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HBJ will be showcased as a posterboy/girl for big stations' development to invite private developers. Already, NDLS, NGP and many other stations are planned for development. Stations with more passenger movement like HWH, CSMT and TNA (Highest number of passengers per day in Mumbai suburban) will come later since per passenger revenue is way too less. Most passengers are MST holders and developer may not earn enough from class passengers (for amenities provided) as too many classy outlets nearby cater the needs.
Unless BPL unleashes some growth oriented projects, it doesn't deserve any more dedicated trains. You are in BPL. Compare living costs in PBH/ALD and you'll find BPL costly, although selectively classy, too. That's not enough reason to attract travelers/migrants. It is like Patna, net exporter of workers. NGP is one of the fastest growing city and may soon achieve metropolitan status. It supports poor to elites. Offers enough earning opportunities to everyone. It is, like BPL very well connected by passing trains. It has very few dedicated trains. But keeping future growth in mind, AJNI and ITW are being developed to cater to increasing passenger demand. In next couple of years, we may see Godhni as another terminal for NGP. That is where more dedicated trains will get allotted.