In my area it is believed that crawling is a very brain developing activity and it is good to crawl early but walk late. Walking is not as brain developing as crawling. Our doctors become crazy if they see any attempt to help to encourage walking earlier. They say that it can cause back problems later. They recommend to avoid too many vertical elements in the vicinity of children

If the child can not walk alone, by himself, it is forbidden to give him a hand and walk with him! If you will try to do it in my country (Latvia), excited moms will run to you with warnings
My first child started to crawl at 8 months, walk at 14 months. The second one performed even better (in eyes of our doctors) - he started to crawl at 7 months, walk at 15
Currently I am reading a bit pseudo scientific literature, "Energy medicine" by Donna Eden. Quote (no references from author):
The Cross Crawl is based on the fact that the left hemisphere of your
brain needs to send information to the right side of your body, and the right
hemisphere needs to send information to the left side. If energy from the left
or right hemisphere is not adequately crossing over to the opposite side of
your body, you cannot access and utilize your brain's full capacity or your
body's full intelligence.
When energy is unable to cross over, it slows down dramatically. It begins
to move in what is referred to as a homolateral pattern-straight up and
down the body-and the body's ability to heal is severely diminished. A homolateral
pattern is natural in newborn babies. Their energy does not yet
cross over: the right hemisphere governs the right side of the body; the left
hemisphere the left side. Crawling establishes the patterning that allows the
energies to cross over from each hemisphere to the opposite side of the body.
This is one of the reasons an infant's learning curve increases exponentially
with the ability to crawl, and children who do not crawl often develop learning
disabilities. Modeled after observations of the importance of crawling for
infants, the Cross Crawl helps your whole system function more effectively,
and it also promotes the healing process. ...