Of course you don't see the need of it, because you aren't in a guild that is supposed to be democratic. The current mechanics, if followed IC on the way it works, would limit all guilds to be dictatorial, so it's even more limiting than what you seems to imply a democratic system would be. In my case, there is a dillema between centralizing OOC most of guild powers on the leader(because in a democracy one cannot take a decision without consulting others) and having a "democracy" by taking decisions based on forum polls, or giving massive autonomies to all members to attempt representing a democracy, though it would be OOC more close to an anarchy then, and would mean the guild could be easily torned off by a single agent provocateur, by bad roleplayers or by "L33Ts".
As I said before, it would be much easier to vote in-game than it is to register in a guild forum to vote for something. Also this would remove the OOC dependence of the guildleader on such democratic groups.
About bad roleplayers, remember that a democracy, specially in guilds as they aren't "the people", can be very elitist. I should remind that Athens "democracy" was only open for its male citizens, that composed a minority of the population, while the majority was excluded. So it's quite possible to prevent that it becomes a "1337 D3m0cr4cY", and a solid recruitment policy also can help much in regards to that. If you keep the bad roleplayers out of your guild, it is very possible to things work out. Thing is, a democracy never works with large amounts of stupid people, unlike a system where all the same stupid people should do was to obey their superiors, for example.
And finally, the OOC stability of guilds is very dull, as @UTM already mentioned. Of course the choice of having elections would be on the guild leader, so now instead of only having dictatorial guild mechanics, you could switch them to democratic as well.