Well there's the meta answer: Oda had not introduced haki at that time. Either because he hadn't gotten all the details figured out yet, or because he chose not to show it off until closer to the timeskip. For an in universe answer, we can only speculate. Cipher Pol agents aren't meant to be soldiers.
Something interesting to note, all CP9 members are said to have observation and armament haki.
He is also a skilled user of the Advanced Armament Haki. It's impressive that Lucci was able to easily take down such an individual. Lucci's latest feats shocked One Piece fans.
The simplest explanation is that that time Oda didn't work with Haki power, so he didn't give them the Haki.
Rokushiki is a special, superhuman martial arts style. It was first introduced being used by the CP9 agents.
Blueno possesses the ability to use Busoshoku and Kenbunshoku Haki. as revealed in his vivre card.
Even though Lucci had Haki when he was still a member of CP9, he still managed to lose to Luffy who didn't have Haki. Needless to say, Luffy is much stronger than Lucci right now and he would beat Lucci to a pulp in a matter of minutes.
In terms of power, Lucci is most certainly several times stronger now than he was before. Furthermore, he has also learned high-level Haki usage and has incorporated that skill with his new Devil Fruit powers. Undoubtedly, Rob Lucci's Devil Fruit awakening makes him incredibly powerful.
Nami's Conqueror's Haki
Once awakened to it, Haki can be manifested as the Color of Observation and the Color of Armament. The Color of Observation grants a certain sixth sense to the user and allows them to sense things like incoming danger, power levels, intent, and emotions, among many other things.
Another member of the Straw Hat Pirates, Brook is an incredibly powerful swordsman who possesses the abilities of the underworld. Being a pirate for an extremely long time, it is questionable how he isn't capable of using Haki already.
The Haki Haki no Mi (覇気覇気) is a Paramecia-type Devil Fruit in which the user is able to see all three types of Haki, as symbolized by a different color.
CP0 is the strongest of all Cipher Pol units, even surpassing the assassination specialists of CP9.
Lucci was the strongest member of the CP9 and just like Kaku, he posed as a shipwright in the Galley-La company. He was the main antagonist of the Enies Lobby arc and was thus inevitably Luffy's rival.
Bajrang Gun is, by far, the strongest technique that Luffy has developed in Gear Fifth so far. This technique sees and makes use of everything that he has got. While using Gear Fifth, Luffy creates a fist big enough to dwarf an entire island and retracts it just like he does in Gear 4th.
CP9, more properly known as Cipher Pol Number 9 (サイファーポールNo.9, Saifā Pōru Nanbā Nain?), is a secret Cipher Pol organization, formed of people able to use the Rokushiki techniques. They are the main antagonist group of the Water 7 Saga, specifically the Water 7 and Enies Lobby Arcs.
Nico Robin is the archaeologist of the Straw Hat Pirates and one of the crew's strongest fighters. While Robin should've been an Observation or Armament Haki user, given that she spent quite a lot of time around those who wield it during the timeskip, she doesn't equip this skill.
Sanji's Haki Types
During the two years he spent at Maiden Island, he trained his usage of both Armament and Observation Haki. Unlike Zoro and Luffy, Sanji wasn't taught this skill by anyone. He managed to learn all by himself and that is certainly an incredible feat.
Sengoku
He is a powerful marine and an important figure like Garp in the One Piece universe. He has the ability to use all three types of haki and is the only person in the Marine who can do that. Sengoku possesses some extreme powers, but we have not seen him use any of his powers until now.
One of the Yonko, Shanks is an extremely powerful pirate. He is the captain of the Red Hair Pirates and is Luffy's idol. Shanks was the first person to use Conqueror's Haki in One Piece.
5 Armament Haki Subtype 4: Internal Destruction
The rarest subtype of Armament Haki, known as Internal Destruction, has only been demonstrated by two characters — Monkey D. Luffy and his mentor, Silvers Rayleigh.
Conqueror's Haki is one of the rarest powers to exist in the One Piece world. Unlike the other two Haki forms, this power isn't accessible by everyone but exists within only a chosen few.
Those who have mastered the fourth form of Haki will be able to manipulate nature as they see fit. They can cause living organisms to grow rapidly or die rapidly (though not resurrect them), and make objects move with the force of their minds, akin to telekinesis.
Haki. How Usopp sees things using Kenbunshoku Haki. Usopp has awakened his Kenbunshoku Haki during the latter half of the Dressrosa revolt, as he was able to see auras of Luffy, Law, and Sugar, who were in the royal palace, from the old King's Plateau near the Corrida Colosseum.
Monkey D. Luffy has mastered all three types of haki, including Kenbunshoku Haki (Observation Haki), Busoshoku Haki (Armament Haki), and Haoshoku Haki (Conqueror's Haki). He can even use several subforms of the hakis, which makes him one of the most powerful haki users in the One Piece world.