They do this on the long straight in Spa as well. I honestly think there is no real rhyme or reason to it because one lap they'll do it, the next lap they won't. (same drivers while in qualifying) Probably done for a moment of relaxation as said before.
"There is a credit card with the Ferrari logo, issued by Santander, which gives the scuderia a % of purchases made with the card...
I would guess that such a serious amount of money would allow them to ignore the constant complains of a car that was nowhere near as bad as their #1 driver tried to sell throughout the season.
Heck, a car on which Massa finishes in the podium or has to lift so that his teammate finishes ahead (As we saw often in the final races of the year) is, by no means, a "bad" car."