You can end any one 'custom'
This is admittedly vague, but it was inspired by two things.
I hear about how much people hate small talk, so wouldn't it be interesting if you could erase the concept of small talk?
I hate the idea of overpriced weddings and engagements, wouldn't it be nice if I could erase that custom?
Of course given how broad the term 'custom' is I'm curious what creative interpretations people here would 'remove'
Basically, the concept of that 'custom' will have never existed, no one except you will remember it having ever existed, this is absolutely exploitable.
However, the custom could re-emerge naturally over time (or quickly if you erase something common sense).