Can one also inherit these timeless teachings without a teacher and without "formally" being part of a Zen Lineage, or just simply by (as someone proposed) sticking a couple of Sutras in your backpack and hiking the "holy trails of Yosemite"? YES! Of course.
But you are also more likely than not going to end up with someone with their own, very personal and half-baked ideas of these teachings ... someone who is convinced they "figured it out" when (without the sounding board and mirror that having a teacher provides) they are skimming the surface or lost in circles and fooling themselves ... someone who thinks they are a diamond when (without the polishing and shaping of the jeweler-teacher's hand) they remain a diamond in the rough unable to bring out the true brilliance of imperfections.
That does not mean, of course, that every product of a "recognized Lineage" will necessarily end up a shining diamond ... certainly not (there are a lot of questionable folks out there with a "robe and a piece of paper certifying their enlightenment"
). However, one is more likely to end up with a well formed "teacher" when the "teacher's teacher" was a gifted teacher who knew how to pass on those teachings, and who had an eye for his students ... could sift out among them the special ones ... could be a good judge of character who could see which students manifested wisdom and compassion and which did not ... all to insure (just a little bit) that things would be left in good hands for the next generation.
I believe there is great value in having some recognized and respected teacher or institution (in modern Dharma Transmission, it is usually a combination of multiple teachers and institutions) approve someone else as a teacher. It is the same reason that you don't want to turn over your heart surgery to anyone with a white coat, but would like to see that the doctor graduated from medical school. It does not mean that the Harvard Graduate doctor will not also screw up your heart transplant, but there is a little level of confidence there that the guy knows what he is doing more than turning your heart surgery over to the butcher in the super market.
Many lineages may have cheapened Dharma Transmission, the more serious lineages tend to take its passing on seriously.
Now, there are many licensed doctors with white coats and fancy degrees who are just butchers, and will do real harm. But there are far more butchers who are just butchers.