Various theories exist for this phenomenon
One answer is that 4.0244 multiplied by pi (3.141) is the exact factor in size that Gargamel is larger than the smurfs and thus this number is considered very unlucky by the smurfs and they refused to pose for this model.
Second theory is this is the price in smurf dollars that the smurfs demanded for modelling for this piece but so far they have priced themselves out of the market. Their talent agent is still trying to negotiate a better deal.
The third and most convincing theory for me is that, as we already know the smurfs exist in a parallel universe. To travel to this parallel universe one must attempt it at warp factor of 4.0244 (it is an exacting science). The problem exists that each time the willing smurf appears in our reality it is immediately whisked off back to its home universe. It is very disconcerting for the participant so therefore after years of trying they just gave up.
Yes I know what you are about to say.. I was up all night worrying about all this and wondering if I should tell you all. I feel I can only reveal the above facts if you agree that it be our little secret.
ps. In the few occasions above (just three in fact) where I didn't know the facts, I just made them up!
One requires a fertile imagination for my job too! Unfortunately when people ask me why is my work late, my audience hasn't been quite as accommodating!