Big bugbear* of mine, this.
Aren't all nicknames conceptual? For example, the concept behind 36ers is Adelaide was founded in 1836.
And the LA Lakers, well, that, um ... is the exception that proves the rule? (Yes, I know they were originally from Minnesota where they have 10,000 lakes - I was striving for - but not reaching - extra comedic value here).
My take is that for years the concept has been 'big, scary sounding' nicknames, with a high proportion of meat-eating animals (Lions, Panthers, Tigers, etc). There's not many herbivore nicknames getting around (ladies and gentlemen, your Toronto...Stegasauruses!).
I've posted about this before, but the current phase we're going through revolves around the letter 's' and teams seemingly being unable to bring themselves to put it at the end of any new nickname.
This 'concept' should go out in a Blaze of Glory. ;)
* 'Bugbear' isn't the worst nickname I've ever heard; ladies and gentlemen, one of your five new Euro NBA franchises, the London Bugbears!