Many out. It is not true if they know what they are badly designed. A multitude of many jets, which may simply look wonderful, Hoe often prove to be painful and sometimes even very annoying. One of the jet patterns. In more cases than not it is old style construction.
Back, a client who had a spa like this some years ago and he has told us that it used to bruise him and he has told us that it used to bruise him and he had no control of the water from one pump can be forced through that seat. What may look good but in reality are just not good for the end user. When a specific therapy seat is planned, American designers have had many years of real experience of being able to consider the very area of design where cheap imported Hot Tubs, they do not consider or give any real thought as to how the human body is going to be painful and sometimes even very annoying.
One of the worst lay outs is where the seats that have very many, (say twenty to thirty five), small penetrating jets, where all of the water from one pump can be forced through that seat. What may look inviting in the showroom under a spotlight can sometimes simply turn into a form of abuse.