Because unfortunately there are limits to what your friends can do for your mental health, but psychologist & psychiatrist are professional careers that specialize in the study of the mind, the health of the mind and how can be restore... The first can study you by evaluating your conduct, personality, perception, thoughts, feelings and emotions towards situations, from that he can orient to you into your rehabilitation... The second, integrate all the above but aggregate the study of your genes and neurology to have a more precise insight of what exactly could be in reality your problem and if can be solved by just a normal therapy or give to you some drugs.
In the case of Yasuka, for years she spend energy and time wasted waiting for a man capable to satisfy her ideals, something that she develop since her father figure and then by the man she knews in her youth which is Noriko's Father that failed her, which tbh, isn't precisely something too healthy, moreover knowing the act Noriko was doing as "good girl" but being bitching and abusing towards MC while she does nothing, could reveal that perhaps she had some grudge towards men. Besides, there are different ppl around the globe, not all of them have many friends and depending how their lives have been, maybe they aren't too good or to afraid to have friends, to forge social connections that are needed for a good mental health too, so, for ppl like that, there are specialists.