For some 'nothing' means a void: an infinite, eternal emptiness, but even such a void has properties - space and time are flexible, and infinity is only one possibility for their structure.
For others 'nothing' means an absence of space and time, but what does that mean? Without space and without time, how can an absence have meaning?
It has been suggested that nothing is unstable, that it will fall apart because of quantum effects and produce universes, but then why are there quantum effects? If we accept the quantum nature of reality, then why is the measure of uncertainty what it is against something else?
The problem of why there is something could well be insoluble because it's not easy to see how we can deal with the subject of existence, because 'existence' isn't a measurable property like size or electrical charge. But, there may be some clue as to what is going on from Relativity. Consider the existence of a beam of light. From the 'point of view' of the beam, there is no reality, because time does not flow for something travelling at the speed of light. Perhaps existence itself is relative: there are no absolutes. There is always a point of view from which anything that we experience as existing doesn't exist at all.
Perhaps 'nothing' is always there, if you look in the right way.