Agree. NER doesn't have to be the dumping ground of NR. Although Marudhar has been extended to BCY, but these trains are the sole dedicated connections to these respective cities from Varanasi. So, they're safe from the extension madness, as of now.
Most of the extended trains in recent times were on the routes where a lot of dedicated connections exist.
And...
more... after yard remodeling, new PFs construction, new pit-lines being added, BSB has enough space, parking yards and maintenance slots to maintain these VBs apart from the regular trains. And they can always change the terminals of regular trains to BSBS and BCY, that's the main reason these stations were redeveloped at such a fast pace.
P.S. I don't understand the logic of BSB-JBP VB, Maihar can help attract tourists, but are there enough end to end passangers who will take that VB?