I don't think they forgot. Trust exp is typically boosted at the end of an expansion:

5.58 for Shadowbringers: https://na.finalfantasyxiv.com/lodes...e8849372cb139e
6.58 for Endwalker: https://na.finalfantasyxiv.com/lodes...67160ef629d31/

Likely SE intends it to be a grind to keep players busy between patches.
Personally I think needing to level Trusts at all is unnecessary and they could have just had the outfits be unlocks for running X amount of dungeons with each Trust.