The Torah presents us with two ways of commemorating an important event. Either we can talk about it (kiddush/havdala, haggada, etc.) or we do the same action our ancestors did (eating matza, dwelling in a sukka, etc.) - these methods of commemoration can be referred to as z'chira and asiya respectively.
There is a third type of commemoration: symbolic. This commemoration would be accomplished by doing an act that is reminiscent of some event. For example, fireworks on the Fourth of July could be viewed as a symbolic commemoration of the War of Independence ("And the rockets' red glare, the bombs bursting in air, Gave proof through the night that our flag was still there.").
The Torah seems to endorse only z'chira and asiya.1 However, the lighting of candles is neither. The miracle of the oil took place in the Beit HaMikdash not our homes. Yet, we light candles in our doorways for eight nights to commemorate the miracle. This is clearly a symbolic commemoration.
Why did the Chakhamim depart from the Torah's normal format and enact a symbolic commemoration? The Greeks had waged a campaign to negate our way of life (as mentioned in the previous post). After the Greeks were defeated the kohanim had a tremendous challenge. The kohanim now had to ensure that the Jews would regain their loyalty to the Beit HaMikdash and the ideals it represented. This is why they instituted the symbolic act of lighting candles outside next to their doorways. They called upon the Jews to demonstrate every year their loyalty to the Beit HaMikdash by lighting candles which bring to mind the menora which stands in the heichal of the Beit HaMikdash.
From a halachik perspective2, the Chachamim could not use either of the methods from the Torah (z'chira or asiya) because of a special challenge that they faced. They could not use asiya because the menora in the Mikdash was lit, not candles in our homes. Likewise, they could not use z'chira because they wanted us to do a public demonstration of loyalty and not recite words privately. Therefore, they had to resort to symbolic commemoration simply because the other two methods could not produce their objective.
Why does the Torah seem to steer clear of symbolic commemoration? To give a very abbreviated answer: it could be that the Torah steers clear of symbolic commemoration because of the important role of symbolism in idolatrous, magical and superstitious practices (ואכמ"ל).
1.Charoset is not a contradiction to what has been said. Charoset is not a zecher l'tit on its own - it functions only in the framework of the mitzva of sippur.
2.The following insight and question were provided, with minor changes, by Danny (in the comments).