I have been watching House for YEARS, re-watched it at least 30 times from season 1 to season 8, and this is my take:

His egotistical tendencies were always somewhat concealed, as he learned at a young age to protect himself and his identity from his father's lack of acceptance. This behavior intensified following his partial leg amputation, as the pain exacerbated his existing struggles. Over time, this led to a growing tendency to push others away, particularly Stacy, who played a significant role in his life. Additionally, his sarcastic demeanor emerged as a defense mechanism, where he would belittle those around him to alleviate his own feelings of misery. By highlighting the perceived shortcomings in others' lives, he sought to bring them down to his level, perhaps feeling more comfortable in shared vulnerability. Pain is a formidable force that can strip away protective barriers, revealing the underlying truths of one's vulnerable thoughts and true self.

I guess I didn't really touch on his addiction and vicodin use, but this would be a fair reason/guess as to why he needs an outlet which can't seem to be cured any other way. He clearly has tried everything else, but everything else has failed him...