Why do philosophers argue more than they think?

As a philosopher, it is psychologically healthy to despise philosophy every now and then.

"Before Socrates, argumentative conversation was repudiated in good society: it was considered bad manners, compromising. The young were warned against it. Furthermore, any presentation of one's motives was distrusted. Honest things, like honest men, do not have to explain themselves so openly." (Nietzsche, Twilight of idols).