I'll explain the reason very simply. Psychologically, a ranked game feels more serious and difficult because you care so much about your score on the leaderboard. Yes. A simple scoring system that can rise and fall has a very strong psychological impact on how you perceive the game. And it makes you REALLY uncomfortable to lose.
I'm just that kind of player, and I'm sure there are many like that. I don't mind playing and losing, trying different decks. But I enjoy playing 1v1 in quick matchmaking, and it's only available in the ranked system. And I really "want" to climb up the leaderboard. This subconsciously makes me a little more nervous and experiences more negative emotions if I lose.
And immediately a second suggestion.
It would be really cool if you could also implement a 2v2 or 3v3 system with a pre-created party. The point is that people play PvP together. And this creates a problem with the lobby system—a group matched against random players, and that's not particularly interesting. Quick matchmaking for teams of 2 and 3 would be a real breath of fresh air in Warno PvP.
I understand that Warno has a small online community, and this mode will be even more dead than 1v1 ranked. But you could make it an "event" by launching it on weekends during the peak online hours.