Binding Vows are one of the most broken moves in Jujutsu Kaisen, given how a sorcerer could attain some ridiculous powers by limiting their potential for a limited time. However, despite this, Binding Vows weren't used as many times as fans presumed. The reason behind this might be simple, and the King of Curses is the prime example.
Throughout the manga, Ryomen Sukuna was only involved in 4 known binding vows, and the majority of them were during his final fight against Jujutsu Tech. The reason behind it might be to avoid the toll this pact could give the user, given how it buffed a user's ability to an unrealistic range. So, the King of Curses utilized them only in scenarios where he knew his victory was guaranteed.
Disclaimer: This article contains potential spoilers from the manga series and expresses the author's opinion.
Jujutsu Kaisen: Why was the use of Binding Vows limited?

The Binding Vow is a pact made between two sorcerers, or by a sorcerer himself, after agreeing on some conditions. Throughout the series, numerous vows were exchanged between sorcerers to test the limits of how far someone could go by limiting or extending their cursed energy to a specified limit.
The first binding vow, which might also be the most crucial in Jujutsu Kaisen, was between Itadori and Yuji. After Yuji's temporary death, he and Sukuna crossed paths, and the King of Curses proposed a Binding Vow, allowing him to take control over his host for a minute. As Itadori was skeptical about this, he and Sukuna had a showdown, and Itadori lost, resulting in the loss of his memory.

Hundreds of chapters later, Sukuna utilized this binding vow to take over Itadori's body and exchanged hosts with Megumi, making him one of the strongest sorcerers. So, fans might get the idea of how overpowered these pacts are. However, if binding vows are that powerful, why not use them all the time?
For instance, if a sorcerer limits his powers to the maximum for an hour, he could become the strongest for an hour. However, the thing that would limit this sorcerer would be the toll created through the binding vow. For instance, using an unrealistic amount of cursed energy might be fun for an hour, but the toll might take the sorcerer's life, as the lost cursed energy needs to be replenished.
So, binding vows were never made without a specific reason. However, why didn't Sukuna, with an almost infinite pool of cursed energy, use binding vows all the time? The reason was simple, he didn't want to take the risk of bearing the toll and always made binding vows whenever he needed them the most.

He stayed silent after making the first binding vow with Itadori Yuji in Jujutsu Kaisen, only activating it when he knew he would utilize the pact to the maximum. During Jujutsu Kaisen's Shinjuku Showdown Arc, when Sukuna's brain was damaged from Gojo's Infinite Void, the King of Curses restricted the use of his brain to only the one untouched by Infinite Void, creating his domain easily.
The other two times when Sukuna formed a pact with himself, he utilized the binding vow to maximize his chances of winning, instead of making hypothetical pacts that might come with lethal tolls. So, Ryomen Sukuna was the epitome of a sorcerer, and his use of binding vows showcased why.
Final Thoughts
Out of all Jujutsu Kaisen deaths that left a bitter taste, Sukuna's might be at the top because, despite being the central antagonist, his way of utilizing cursed energy was unique. Sadly, a binding vow couldn't save him from getting defeated, but became the reason for his defeat as Itadori Yuji's pact to himself restricted his innate cursed technique to only hit the boundary of a host and parasite.
Related Links
- Jujutsu Kaisen promotes volume 27's release via live action trailer
- Jujutsu Kaisen just confirmed Sukuna's status as the "strongest sorcerer'
- Jujutsu Kaisen: Sukuna as the "strongest sorcerer in history" turns a simple concept into the deadliest cursed technique