Clavia have a section called Legacy,on their product webpage,which is where the older(out of production) products are able to be viewed and read about,like most companies do,you can't keep everything current,so some products are just catalogued in a sub product page,most companies will do this.
Roland and Korg have reworked there classics 90s stuff but in software form,,its great having access to those sounds again because not everyone wants a room full of hardware anymore,there would be no real point in bringing back the hardware as there are plenty of originals still around that it makes no financial sense to release a replication model of an older product,certainly in Korgs case the revival of the Old Wavestation to the newer Wavestate,has been an interesting venture,but they have reworked its form factor and aimed it towards the majority of current musicians who need smaller easy to transport gear,i doubt they would have been so successful just reviving the original Wavestation as it was,from a financial point why would anyone purchase something they can get at a fraction of the price secondhand.
If you saw a 2X in a shop it was probably a trade in/Secondhand from a customer purchasing something newer,they don't make them anymore,and have been out of production for a many number of years so doubt it was a Demo product unless the shop have kept it for a very long time,but a lot of musical instrument sellers do trade ins for newer gear,my local retailer has some older bits of synth gear from time to time that people trade in and they put them side by side with the new products,obviously to sell them on.
I don't understand why you would want to see a revival of older Nord products,there are plenty of on line demos/Videos of older instruments now anyway so,the info is out there for you to see and hear older gear,Clavia don't seem to be the sort of Company whereby they re-release an older product in exact form,perhaps they tend to build on the older technology bringing out a newer version with enhanced features,rather than a direct revival,closest I suppose they did was the Nord Lead 2 to 2X enhancement being essentially the same machine but with expanded storage.
For me there is a lot of crossover with all Nord Products anyway,so other than a few updates to things,your essentially getting the heritage of a legacy product but with newer features when you buy a newer model.
I have an original Nord Lead and also the more recent Nord Lead 4 both although may have slightly subtle tone/Oscillator differences,they come from the same heritage so there isn't that much of a difference to say that the older model is superior or better,the Newer model can do everything the older one can and more,the only difference is the code of the original Model which some say makes it sound slightly better than the newer models,but that is subjective.
I am more interested in newer technology rather than looking back all the time,I've used all the older Nords and still own several of them so there is nothing that excites me to want to see Clavia bring them back,theres plenty of them around to buy if you want that particular Model,the only thing I would like to see is perhaps the Nord Lead 3 revived,because I'd like to see a newer FM based synth from Nord,not just the fixed operators they include in many of the newer models,for me the NL3 was a very unique model,which enhanced the traditional VA model and gave it more scope from the traditional Nord Synth line.
And yes, business is the answer to this. But I wouldn't expect them only introducing the new ones to artists who are beginning with synths or want more rougher sounds.