Something like the DAM doesn't really need a display, but given the price of the other Dye markers it makes sense to expect them to have what are now standard features. Displays aren't necessary on any marker, they're a "nice to have". When somebody spends $1200 on a marker, they expect those nice to have features.
Anyways that's a speedball discussion
I sometimes think it would be nice to have a display on a milsim marker, but under the grip so it's invisible until you want it. Makes tuning, mode setup etc. muchos easier. Again though it's not really needed. Just means less faffing about. Kinda like tool less hoppers and so on. The less tool and manuals you need, the better.