Boundaries are useful as a conceptual shorthand, but we may place too much reliance on these imaginary lines. Putting all the emphasis on the shorthand keeps you from thinking about the full content which is being abbreviated.
Consider property boundaries as the archetypical example. By drawing imaginary lines in the sand (or the clay or the stone) we conveniently limit many causes of disputes among neighbors. My cows will not eat up your grain if I heed the boundary. Your tractor will not plough up my corn. My quarry will not take the rock from under your house. These are the reasons boundaries were drawn.
On the other hand, an imaginary line does little to keep your wild parties from disrupting my sleep or my draining cesspool from poisoning your well. The smoke from your fire can't be blocked by a fence. Squirrels attracted by my walnuts will not avoid your flower garden. The property boundary is useful, but does not encapsulate the fullness of what it means to be neighbors.
The same may be said for more the abstract boundaries which society sets up in law or custom. Some behavioral boundaries are considered more significant than even property boundaries because they regulate behavior which affect people in deep and lasting ways.
There is a boundary which keeps therapists from having sex with their patients; crossing that boundary is a serious breach but the boundary does not fully define the proper relationship. The boundary is merely a shorthand for a very egregious deviation from the proper relationship between therapist and patient: In real human psyches, it is not possible to engage in intimate, passionate behavior and yet remain the dispassionate observer. In real human beings, it is not possible to disentangle any possible positive motivations from the exercise of power by the therapist over a vulnerable patient. But we don't want the therapist only to avoid egregious deviation. We don't blindly accept all behavior within the boundaries. What we want is for the therapist to maintain clinical clarity and to exercise influence over the patient only to the extent that that influence is very likely to improve the patient's life. The shorthand of the boundary is useful, but only as a way to narrow our discussion to a smaller realm of behavior which is more likely to be beneficial.
Our society is particularly adept at drawing certain boundaries. For example, there are many boundaries in relation to sex, not just the one that applies to therapists. You don't have sex with cats. You don't have sex with children. You don't have sex with people who are unconscious. Well, of course not. All such behavior is hurtful. If we become preoccupied with these sexual boundaries, however, what have we become preoccupied with? Having sex.
In doing this we place ourselves in the position of a yound child who is told, "Don't touch that paint! It's still wet!" Is it really wet? What does wet paint feel like? If I touch the wet paint, what will happen? Does it stick to me? or change color? or fall off the wall? Even as an adult I can't think about much besides touching the paint, now that the behavioral boundary has been made the focus of attention.
When you are walking in the woods, the normal and natural behavior is to place you feet on the earth. What else would you do? If there is a log on the ground, you might step on the log, but typically it isn't as stable as the earth beneath. Once I built a set of steps in the woods by staking a series of small logs across a steeper stretch of the path and leveling the earth between them. When the children returned the next day, I told them, "Don't step on the logs!" Everyone said, "Where can we step then?" On the dirt, of course, like you normally would; but I had unintentionally distracted them from the obvious to look only at the exceptional.
Boundaries are useful as shorthand, but they can easily distract us from considering the real issues about living together. We may need to say, "Don't step on the log," but it should always be in the context of saying, "Step on the earth. Put your feet where the path is most stable." We may need to say, "Don't let your livestock into your neighbors' field," but it should be in the context of saying, "Take care of your animals and make sure you have the resources to feed them."