You have to keep in mind that your scope of practice isn’t a set of “laws.” There really isn’t anything to stop any of us from acting outside of our scope. However, the organization that gives us our certificates will deny us of insurance and/or support should be be caught practicing outside of our scope (typically this will be the case when some legal action arises, like when a client files a lawsuit for being injured while performing an exercise under your supervision).
The scope of practice should be viewed as a set of boundaries govern by the level of education we receive for that certification (or as a prerequisite for that certification). If we follow our scope, then we are acting on information within what we were trained for. Generally, the organizations that has their members follow a scope of practice are those that holds themselves to a high standard. They are also the ones that can provide insurance to their members.
This is something to consider when potential clients asks why they should pick you over someone with a weekend certification. You hold yourself to a high standard, understand that you don’t know everything and will seek help from other professionals to fill in what you don’t know, and ultimately keep your clients safe while they work towards their goal(s). If you stay true to that, you’re likely to retain the clients that you want.