Why? It hasn't been a problem for Lamborghini. Nor is it a problem for rapidly growing FIAT brand Maseratiwi not to have any real motorsport presence. This is just an urban myth. Ferrari could survive very well (and be far more profitable) without spending a fortune on F1.
First, they are very different companies in size: in 2013 Lamborghini sold about 2100 cars in comparison to Ferrari's 7000 and their revenues were 508 M€ vs 2.3B€ respectively.
Secondly, they pursue different stategies where Lamborghini is trying to get market share whereas Ferrari decided to limit and reduce the sales numbers of the cars to maintain more exclusivity in 2013 and succeeded by that to lift unit value and profitability up to 367M€ and they are expected to improve further this year. Lamborghini has not published their profitability in 2013 but when they last did it in 2005 it was not very good (less than 5 M€)
So in my mind staying in a top tear motorsports is essential to Ferrari strategy to maintain the exclusivity aspect and by no means an urban myth. Of course you are correct that they may change the strategy but it is anybody's guess would that be as successful.
Edit: Concerning Maserati, their strategy is not relevant to Ferrari since they operate in different business segments where Ferrari is in the Luxury business and Maserati in the Premium segment, as confirmed by Maserati CEO.
Edited by Jvr, 09 August 2014 - 14:30.