1. I think the point is they learn the more difficult skill first, which is balancing. It's low enough to the ground that the kid can balance with their feet, but they will naturally start picking up their feet when they get some momentum and speed going. I think it's a much less stressful way to learn riding a bike compared to knowing mommy-or-daddy-might-let-go-and-I-will-fall school of training.
2. A very quick google search got me this¹. More than half the balance bikes on there have brakes. I've seen similar on other bike websites. I agree it's irresponsible to not have brakes, especially for the bigger kid models.
I have a 7 month old now. I want to get her on a balance bike before the end of the year, or maybe start with a trike. Exclusively indoors, or under very strict supervision from me if we are anywhere outside. As soon as she's big enough, she'll get the smallest "big" bike where I have removed the pedals, but we have the front and back brakes present. Then she'll continue balance-biking on there till she's ready for the pedals.