When there is a negative sample (for example transit network trouble) the score drops a lot. After a positive monitoring sample the score of a server increases only with small quantity. What is the reasoning behind that asymmetry?
To quickly remove the unresponsive server. If it takes hours to remove a (possibly) defective server, clients will receive no time from this server in this rather long period. After the removal, the affected server must show its healthiness long enough to be included in the pool again.