I'm actually working on a shorter (30 minute) roguelike game for mobile. Part of my monetization and retention strategy relies on the feeling of "progress" that players can get by unlocking new things. But I don't want to let that make the game easy - just different.

If I let my players see a new "hero" or "level" they can unlock by winning or accumulating meta-game currency - they'll come back more times to play through the game. If there's nothing to unlock, they might play until they win 3-4 times, get bored, and churn. If they can unlock a new hero, or dungeon every 3-4 wins, then they have a much higher chance to keep playing the next 3-4 times, because suddenly when they were about to churn they unlocked a new way of playing the game. And that also gives me time and a strategy to release new content - while players are playing through the 5 or 6 heros or 2 or 3 dungeons I release with, I can design new ones, and update those into the game.

I also have a strong incentive to keep the heros balanced. If I don't people will only want to play with the strongest one. Since there's effectively less diversity in available playstyles, there's less effective content that the players will be wanting to play through, so they'll get bored faster. If they get bored before I release new content, they'll leave.

I also want to have a list of items/enemies seen in the game, and make this take a while to fill up. One way I could make it take a while to fill is by having new items/enemies be released as the player plays more. Instead of overloading the player with content in their earlier playthroughs, which could lead to not hooking them, they are ramped up over a longer period of time and are always finding new things in the dungeon. I could also even add new items and enemies retroactively to old dungeons with new content like this, all without hurting the new player experience.

So TL;DR, I want to have soft-progression because it will keep people entertained longer. Longer entertainment means more money.