I think it might be a "fashion thing" however honestly look at the tc4, it hasnt had the results. The tc3 was a factor at every race it went to in mod and stock, the tc4 hasnt been one yet. Alot of the stock carpet guys used to run tc3's, alot tried tc4's last year in cleveland, then showed up at the novak race with an xray (i did as well after driving one, the thing drives itself. I hadnt been in a B main in stock sedan until i got my xray, i ended up bq'ing and winning the b main by half a lap at the novak race in stock foam).
For me I could care less if the car is fashionable or not, I care that it works. While the FK05 isnt the easiest car to work on (taking out the diff takes a few minutes longer than a tc3, but it isnt really that bad), it is defently faster than the tc4 on the track. (btw IMO, the fk04 is the best car, second to the worlds car that was never released, by xray, espically in stock and 19t or at least in stock and 19t foam)
The losi has shown itself to do pretty well at some races (cleveland last year) on carpet, however without a large stock team like xray or corrally it is underrepresnted in some areas.