If we draw the conclusions from a quick reconstruction of the presence of Democritean doxai in Sextus, we could underline that he seems to use them with the precise (and often explicit) intention of reaching at least two purposes, both functional to the attitude he constantly shows vis-à-vis philosophic past. These purposes are — it seems to me — the following:
a. the first one, that of taking advantage of D.'s doctrines as an integrating part of the diaphoniai that he builds (or that he inherits from the Pyrrhonian tradition which preceded him), always presenting D. as a Dogmatist among other Dogmatists;
b. the second one, immediately consequent to the first one, that of denying to D. any role as ancestor of true skepsis and therefore of stressing the purity of the Pyrrhonian philosophic pedigree. He defends it from any dangerous intrusion and offers a strongly 'exclusive' reading of the history of philosophy preceding him, quite different from the one provided by philosophic historiography fostered by Academic scepticism, which had sistematically sought forerunners, above all among the so-called Presocratics.
Spinelli, Emidio, "On Using the Past in Sextus Empiricus: The Case of Democritus" (1996). The Society for Ancient Greek Philosophy Newsletter. 203.