However you only need one diversion (expensive) and all that saving plus some, is lost.
It's a statistic question. If no one diverts on a basis period (it depends from company size, fleet, etc.) company gains, if not it looses.
12 months ago if you flight planned to Mumbai for eg.,with 30 mins holding fuel, you would have a 50/50 chance of a divert.
For these reason some destn have specific extra fuel accordingly to particular environment, atc, arrival time, etc.
It does not mean that we can continue to carry on tons for dad and mummy as in the good old times.
I agree, and i used to work as, with 757jetjockey.