If barriers harm more than abuse then abuse should be accepted.
"The optimal amount of fraud is non-zero"
The optimal number of (minor) crashes when training for a mountain bike race is non-zero. If you never crash, you cannot be sure you were going fast enough around that turn.
People are risk averse, so a known cost is preferable, even if expectedly higher than dealing with abuse. This is in part why insurance is so profitable.
If it's an error, you correct and accept errors as the cost of doing business.