Keeping in mind the aforementioned black points, the halos are just one part of this. Halos are the black eye rims. When the rims are solid pitch black, and circle around the entire eye without any fading or disconnection, these would be halos.
The super rich black that encircles the eye, along with the very dark eyes of a Maltese, create the appearance of having very large eyes. This is a desired physical trait. And as explained above, since black eye rims are part of the standard, it is favorable when judging.
For any dog breed, there are always show quality dogs and pet quality dogs. Many breeders will not even sell their show quality dogs, or at least those destined to become champions in the ring. And if they are sold, prices may be much higher than otherwise.
While all reputable breeders strive to meet the breed standard, it is a guideline for goals. It is not always attainable. And therefore, it cannot and should not be expected for every single pet Maltese.
Ideally, if breeding, you would want to only pair Maltese that have strong halos and strong black points. This advances the generations going forward to carry these preferred traits.
But, even with careful breeding selection, genes can carry from 5 generations back. So, it is perfectly common for pet Maltese to have most
of their black points but to have those thick, black eye rims that are the halos.