Aside from the question of why is just that the companies are moving forward with new ideas. Not many instruments/music gear really become something as ubiquitous as a gibson les paul, or a strat. Elektron progressed with the OT and the Analog 4, and now the Digitone.
Those devices aren’t that popular, very niche. Sure someone will always buy them but these days it’s short lived as far as major continual sales. A lot of money goes into rehashing production of something that probably used a lot of outdated parts, not that it would be to hard to update but the OT really supersedes the MD.
Sure the MD has the dedicated machines for drum sounds, but it’s not like the OT can’t shape the same basic tone into a million different things it self, irregardless if it’s a dedicated digital drum synth in your mind or not it’s still as capable of recreating anything the MD does even with less LFO’s parameter locking is the same thing and resampling allows you to modulate it over and over.
The monomahine is cool but I think more hype. The DN may be lesser than the monomachine feature wise, I’m not sure but still not much difference is there as to what they do. Yeah, filter, overall character, may be different but is the MNM really worth the gut wrenching price, only you can decide that one. What I just saw, nah, no way for a digital synth, OT does so much more over that thing any day.