I'm not disagreeing with you in any way @JustKeepBuilding. It's great that you help families free of charge (I do too). There are resources available, the information on the IPSEA website is brilliant (as is their training if people can afford to access it).
I just know, from what I do, that there are an awful lot of parents who can't access them. Or maybe they could, but they don't even know they exist. I meet parents who have disabilities themselves, who are so overwhelmed by their lives and caring for their child/children with SEND themselves, who maybe also have their own learning difficulty or disability. None of these parents would have the first clue about how to access these spaces. It's not uncommon. They might not have a laptop or tablet, or be very computer literate, or be able to fill out the paperwork properly (especially an EHCNA!). They don't know what their children's rights are or where to access help that they're not automatically excluded from because they can't afford it.
I try my best to empower them with some knowledge and confidence, show them where to go and what to do but often what these individuals need is someone to handhold them through the entire process or more often, in all honesty, for someone to do it all for them. Without paying, you're hard pushed to find someone that will do that especially on a larger scale.
So it continues. The children (like my own, i have no problem in admitting it and perhaps this is why I give my time for free to help other families, because the unfairness rankles) who have parents who are qualified, educated, confident, with time to dedicate to advocating for their child, computer literate and able to afford things like independent assessments when the local authority is crap etc etc etc will generally receive better levels of support. My child's needs are met in school because I have (as the OP describes) fought tooth and nail for them to be. There are children in their class who most definitely need similar levels of support but do not have it. I know the parents fairly well, and I make an educated guess as to why this is.
What should happen is needs are identified and families should not need specialised knowledge, help and support because 'the system' should take care of it all in a fair and proper way. The system does not. But we are where we are and we do what we can, I suppose.