True, but lets not forget another non trivial one: advertising. I'm lucky if I can spot a new board discussed in a few sites, while every time a new PI is launched, the news resonates like someone set their feet on Mars. If manufacturers want to build a community and have more developers/ports/bugfixes etc. they should allocate some resources where it's appropriate. Not easy since the PI is pushed by Broadcom themselves, I know.
Also, I would avoid the term "clones", which gives a bad impression of the products. There's no such thing as a Raspberry PI clone, unless having similarly placed connectors in some models counts as cloning. The hardware is (thankfully) vastly different. Also, Broadcom doesn't sell the PI processors to anyone else ensuring that cloning them is impossible, as is building any product using the same technology, short of hosting it in the form of a compute module, which may not be the ideal/cheaper solution in many contexts. Not a big issue since there are much more powerful platforms out there, but few know about them for the above reason.
Personally, if I see an interesting board, my 1st and 2nd stops to see if and how well they are supported are the Armbian and DietPI boards and forums (other suggestions highly welcome!).