Spirituality on these particular cards/sheets, refers to their openmindedness and connection to a non-materialistic world (and things like that. Such as gods, aliens, pre-destined fates, etc.)
And why is his so low, actually, literally absent?
Because he's been very unlucky.
EDIT: Switched spirituality with Stamina. Will leave his tragic stories up for your amusement though
He was married the first time at the age of 22, with who was believed to be the love of his life. They loved each other whole heartedly, and even had a daughter together. Though, happiness wasn't something that was going to last, and one unfortunate night, his wife was killed. He tried to raise their daughter on his own, but as she grew, she reminded him more and more of the love he lost, and he couldn't bear it. He couldn't stand looking at her, because he felt like his heart was breaking everytime he did so, and thus he had to give her up, kindly asking for one of his relatives to take her into their family and raise her instead.
Later, after having finally managed to deal with the loss of his first wife and true love of his life, he met someone new, whom he believed could be a more than acceptable and decent new wife. They were in love, no doubt, but it was soon to be realized that it was more like, one of those teenage loves. Something that felt good but wasn't meant to last. They thought it could be overcome, and got married anyway. They stayed around each other, dealing with the differences between them and had a decent marriage with one another, even getting a daughter and a son together, but Raul being the introverted and quite withdrawn guy that he became after his first wife's death, quickly started to annoy his wife. He grew avoidant, refusing to answer questions about his past, and downright snapped at her when she was pestering him about either getting help with it, or trying to talk him into telling her the truth.
He didn't intend on hurting her, or driving her out, but his sharp tone, and his short temper got the better of him, and while he wasn't physically harming her, he gradually made her mental helath go down. He was draining to be around, he was difficult. He cared so much but he couldn't help himself. Eventually they figured out that it just wasn't meant to be, and that even if they tried to keep their marriage alive, it wouldn't be a happy one. Their family would end up being broken at this rate, and this lead to the inevitable divorce.
The wife got the custody of the children, though freely allowing them to choose how frequent or how little they'd want to see and be around their father. The kids blamed their father for the divorce and for tearing the family apart, and Raul just took the blame and accepted to be their scapegoat.
now, he doesn't see his children very often, and of course he's paying for child support to his ex-wife, despite her re-marrying with a younger fellow, with an obviously less depressing and draining aura than Raul.
However, all of those sad and even heartbreaking events, he has dismissed all beliefs and openmindedness towards a non-materialistic world, as well as the supernatural and everything along those lines. He refuses to believe the existense of gods, aliens, angels, demons... Everything.
Also, it is known that it was after the death of his true love that he started to have a short temper. Having a difficult time dealing with problems, and even more so with dealing with ill-natured individuals, whether with or without sassy attitudes. Though sass and mockery from their side, doesn't aid them well in dealing with Raul, as he will just yell at them, throw them out, and even be likely to refuse helping them.
He is known to throw out ungrateful and/or rude patients, bluntly telling them off, telling them that if they want answers and want help, they are going to have to search for another doctor. The only patient he has not been throwing out, though still treating him harshly when he gets sassy or otherwise out of line, is Ashley.
Given shared tragedies, granted in different ways, they see each other, and despite being as different as they are, they acknowledge each other to some other extend than just patient-doctor, or even friendship.
Furthermore Raul is one of Angel's very few sympathizers, and one of the only ones to know where Ashley went hiding, after fleeing from his pursuers.
A fun fact with Raul is, that he utterly despises firearms. Regardless of what kind they are, it doesn't matter. Since his first wife was shot, he's never taken a liking to those weapons, and even refuses to hold one, bluntly stating that he would "Rather die than defending himself with one of those atrocious tools of destruction." - Not that he tries to actively keep Ashley from using fire arms. He is well aware of Ashley's life threatening situation as well as how many wants him dead, and supports the idea of Ashley protecting himself, which Raul believes that AShley is more than capable of (Whether with or without weapons).