The education of lay people starts with language though.
From another perspective, allowing the notion that one unqualified person can instigate a direct section also sets up a frustrating dynamic with professionals. There is already a huge issue with communication within said professionals and constraints they operate within such as the MHA.
It's all well and good if a HCP or psychiatrist has good people skills, but if they don't you get potential defensiveness all round.
"I want my relative sectioned because x,y,z."
"Woah, you're not qualified to make that call, and we have to assess things and factor in your possible motivation, sectioning is a last resort"
As opposed to:
"I'm really worried about mu relative because x,y z how should this be addressed"
"These are the steps, possible routes to support and until deemed otherwise, your relative has the right to be involved which by law must be respected, however we'll try and help as best we can".
The OP has highlighted quite rightly, that the immediate jump to "sectioning" as some kind of one size fits all solution to mental health crisis has become embedded in current thinking, and I do think changing that is important for all those involved in mental health care, be they patients, professionals or understandably distressed loved ones.