For some reason I find it absolutely fascinating how this is what he picked to focus on? It doesn’t bother him not having a house or an income or not being deemed responsible enough to have his own money. But god forbid he doesn’t have a girlfriend.
Isn't it amusing?
His Love Quest is his one cause. It is what he does, what he worries about, what torments him: a spectacular, decades long history of romantic failure and rejection. He has 99 problems, and only cares about the bitch one.
He's like a cartoon character in this respect, always producing the same gags.
He had been lonely and single for 99.9% of his life.
As for why he focusses on it, I offer two complimentary theories.
One, it's the issue that speaks most directly to his self esteem and his sense of himself as a failure. Since the age of 6, girls have spurned him, boys have laughed at him. His inceldom may represent his general failure to build a life worth living, or praising. If he gets the bae, the rest will right itself, he reasons. Parents won't be ashamed (he'll give them grandkids!), women will praise him, men will envy him. Plus, he'll have someone to boss around and take care of him (and anally torture).
Lucas will finally be vindicated, and his 40 years won't be in vain.
Second, with so many problems, how does one tackle any of them? He must be overwhelmed and lost in the face of all the shortcomings he has to deal with. Virtually all everything about his life is a disaster. Physical health, education, finances, mental health, living arrangements, relationships, everything is fucked. It's just too much to tackle, so he focusses on the discrete challenge of the Love Quest.