It gets preferential treatment because it is the only team which has competed every year since F1 began in 1950 and has won more titles than any of its rivals. Ferrari is also the only car manufacturer involved with F1 which directly signs contracts with the F1 Group rather than using a subsidiary company to do so. This gives recourse directly to Ferrari itself if the contract is breached whereas a subsidiary company could easily be shut down.
So important is Ferrari's status as the longest standing team that it even has control over the race weekend. Page 177 of the prospectus reveals that the F1 Group has "agreed to give to the Longest Standing Team, if it is a manufacturer of GT racing cars, a right of first refusal to run an international motor sport series for its cars as a support event (i.e. to be included in the track programme of an Event as a support event to the World Championship) on terms and conditions no less favourable to the Longest Standing Team than those granted to other entities."