Sometimes aiming for safe sanitation might also make it less safe in the short to medium term. For example sewers without treatment yet, or septic tanks with no emptying service etc.

Sometimes it can also lead to situations where part of the population is better off, while others suffer as dumpsites for insufficiently treated waste.

Of course that isn't supposed to happen with safe sanitation, but in the "real world" many places get stuck somewhere along the way at least for some time.