First: because there is absolutely nothing they can do about it. Scammers can use any picture: mine, yours, anybody's, and nobody can stop them.
Second: They get upset, and many of them DO NOT want scam victims to bother them. One man complained that victims found his real profile with a phone number and started calling his house and bothering his wife after midnight.
Third: Many of them, instead of going after scammers and dating sites with fake profiles start going after scamlists and threaten them with lawsuits. They don't understand it's scammers who abuse their pics, they think it's scamlists who violate their copyrights.
Fourth: Victims confuse real and fake profiles, and either warn just another scammer thinking he is RPO or insult an innocent RPO thinking he is a scammer. It's a mess.
Just report your scammer on romanescam and warn other victims, this will do much more good than searching for RPO.