I realize the question posed is "what do you see here"...but what I see "here"...is a bunch of amateur armchair engineers...!
There is really no information on the actual mix of the concrete for all we know it could have been a high PSI mix to allow for a wet, easy to place pour...it could also have had fiber along with a rich Portland content which greatly increases the tinsel strength of the slab eliminating the need for wire etc...
As for the rebar...for the most part unless there is a deeper "stiffener" required for specific load bearing purposes etc. most slabs do not even require a rebar grid (wire mesh and or fiber is all that is required to obtain the required strength)...there are millions of basic floor slabs designed by engineers and architects where no rebar was/is required..in a majority of cases rebar for this type of application is merely overkill...
I'm not saying the above is the case it does look like a lousy, amateur job but you can't always base things on the way they appear...
Control joints are often sawed shortly after the pour is made...