My good friend's mom was mom to all of us kids around, and also to her husband. They both loved it, she provided him with love and care and he was kind of dependent on her to organize his life, so he was always with her and loved her like no other woman. He had a lot of time to do some science stuff, too (he got money from patents, fair enough). She died, he is lost without her even after many years. There are women like this and Beta looks exactly like one of them. It's mom vibe which attracts children of any age to them.
Axl ain't normal. He is one of the adults with most childlike soul I've ever seen, and that's what makes his presence and performance so outstanding. Most people loose this magic when growing up, when they reach puberty or so. They excel in schedules and repetitive stuff. They can't do magic anymore, to pull the things out of the blue. Many normies actually like to care about magic people, because magic people can do magic then. With their presence, with their wit and sharpness, it's nurturing itself, even without shitload of money, luxury house and traveling... I don't think Axl couldn't take care of himself, he most probably can do all the chores, but there's always someone to do that for him. Axl's mind works different, it's unorganized and I bet he hates repetition, so there are always people around who are better in this. You cannot switch your unorganized, creative mind to some "normal" operating mode just because it would be better for next three hours and then go back to creative, funny, witty unusual critter to do the things normal people cannot do and perceive what they don't. Package deal.
I still insist on Beta actually saving Axl during his recluse/depression years by the way of care she could give him, the missing mother care, solid point, unconditional love he craved for when he was two. Normal woman couldn't give that to him, Beta didn't kiss him passionately, she kissed him goodnight. Basically, Axl is a default child, Beta is a default mom, they met each other and clicked. Rest are details. They might get married like many pairs with mom-child dynamics, yet they left it in this friends/family state, maybe to avoid sexual tension in this particular relationship, they know, me not. I've seen adults around me in so ridiculous relationships that it's not much weird to me. Axl is stable and happy, anything else?