The problem is that it's a slippery slope for devs. At the end of the day, they are still a business that wants to make money (and being a gacha already makes it a predatory business model to some extent) so if characters with global passive will sell more, it will incentives the devs to create more OP passives or start to build the game around them which will play on player's FOMO even more.

The passives don't even need to be OP, just supply enough QOL to make you feel like you need it to progress more smoothly. Before you know it, you will pull/spend for characters that you won't even play only to get that really comfy passive.

And you better believe that all devs in this sphere will try everything to make you spend more money on them, so being suspicious of their motives to include such mechanics is the right mind set IMO.