We considered the appeal of this field to these case managers: An interest in reaching out to other people who went through a similar struggle or trauma. Perhaps give back after they got help themselves.
It may be bonding or inspiring for a client to know a case manager shares his experience but the latter wouldn't necessarily disclose this to his client.
On the other hand, having had a specific experience a worker may be biased and expect to see the same reactions in other people as she herself experienced. This may lead her to fail to acknowledge or entertain a different reaction or client's choice than what she herself made.
Is a case manager less effective in working with a survivor of trauma or addiction if she herself hasn't shared that experience? I don't think so. A professional must learn the theories behind trauma/addiction and treatment (and continue to read up on this as new research comes out) to learn how to effectively work with a client. Experience with clients sharpen a professional's ability to work effectively with them. Patience and an attitude towards working together with the client are more important components of an effective professional relationship than sharing a common background.
* Recovery is how I can best describe people dealing with trauma, grief, sexual/violent assualt, substance/alcohol abuse.