Time-Turners can cause serious consequences and are of limited use.
It's pretty clear that Time-Turners aren't something to be used lightly. While the Dark Lord was willing to take certain risks, like creating Horcruxes, he did that to ensure his immortality so would have considered it a worthwhile risk.
“Exactly! You wouldn’t understand, you might even attack yourself! Don’t you see? Professor McGonagall told me what awful things have happened when wizards have meddled with time … loads of them ended up killing their past or future selves by mistake!”
- Harry Potter and the Prisoner of Azkaban, Chapter 21 (Hermione's Secret)
While the Dark Lord cared little for other wizards, he greatly feared death. If he knew that using the Time-Turner would likely result in his own demise, he would likely avoid it. The Dark Lord is cunning and calculating, and everything he's done is to ensure himself immortality and power. Every risk he's taken, everything he's done since he was a teenager, has been in pursuit of that goal. He wouldn't want to do something that puts all that at risk, he's anything but suicidal. He probably wouldn't have considered the risk of using one worth the possible reward, especially as they have only limited uses.
A writing by J.K. Rowling on Pottermore further elaborates on the dangers of time-travel.
As our investigations currently stand, the longest period that may be relived without the possibility of serious harm to the traveller or to time itself is around five hours. We have been able to encase single Hour-Reversal Charms, which are unstable and benefit from containment, in small, enchanted hour-glasses that may be worn around a witch or wizard’s neck and revolved according to the number of hours the user wishes to relive.
- Time-Turner (Pottermore)
Traveling in time even a small amount is highly risky, but any attempt to travel more than a few hours does severe damage to the wizard attempting it - this is a risk the Dark Lord wouldn’t want to take with his own life.
All attempts to travel back further than a few hours have resulted in catastrophic harm to the witch or wizard involved. It was not realised for many years why time travellers over great distances never survived their journeys. All such experiments have been abandoned since 1899, when Eloise Mintumble became trapped, for a period of five days, in the year 1402. Now we understand that her body had aged five centuries in its return to the present and, irreparably damaged, she died in St Mungo’s Hospital for Magical Maladies and Injuries shortly after we managed to retrieve her.
- Time-Turner (Pottermore)
Their use is tightly controlled by the Ministry because of the inherent danger they pose.
While not as potentially dangerous as skipping five centuries, the re-use of a single hour can still have dramatic consequences and the Ministry of Magic seeks the strictest guarantees if it permits the use of these rare and powerful objects.
- Time-Turner (Pottermore)
The Dark Lord wouldn’t care about how he affects the rest of the world, but time traveling is very dangerous for the wizard attempting it, and the Dark Lord doesn’t risk his own life.
Also, the Dark Lord would consider it admitting a failure to undo an action taken in the past.
Remember, Lord Voldemort considered himself a very powerful and intelligent wizard. He would not want to do anything that implies he made a mistake or missed something in the past, and actually reversing time to change events seems like a very big admission that he had let something big enough that it merits changing happen to begin with.
