@richrf,
It seems to me that the entire problem revolves around the human tendency to require a cause for every phenomenon. The question, 'why is there something rather than nothing?' does indeed seem to rest on the assumption that
nothing is somehow more fundemental than
something: i.e. that nothing preceeded something and is perhaps causal thereof. That erroneous assumption arises through the application of what we observe in ordinary life (one event leading to or causing another) to an abstraction. If one thing/event/phenomeon must always precede and cause another, then logically, some thing/event/phenomena has to preceed and be the cause of
everything. However, if we are asking what preceeded or caused
everything, that cannot be a thing in the same sense as the various things which we are collectively calling
everything, because then it would be included in the group
'everything.' Therefore, we require something outside everything, something which is not a thing, and that is
nothing. What is nothing? The logical antithesis of 'thing'. It does not exist, it's an abstraction, an ideal, and one without any sense. The word means nothing (no pun intended).
We can provide a logical antithesis of something else, e.g. unshirt (antithesis to shirt), but that word doesn't mean anything; the fact that we can formulate this antithesis doesn't mean that it actually refers to something in the same way that shirt does. Unshirt exists only insofar as it is a logical derivative of the concept shirt, which refers to something really existent.
So, why does something exist instead or nothing? Because 'nothing' is a meaningless term, a logical ghost, which refers to nothing that exists. It only exists (as a term or thought) in relation to something. Thus, as something must come before nothing (because 'nothing' is a just a logical antithesis of something), it is nonsensical to ask the question. Reworded, the question runs 'why does that-which-exists exist instead of
not-what-exists?' with the phrase 'not what exists' literally having no meaning other than the term 'not' + 'what exists.' It's a language problem.