Since Raditz’s arrival on Earth, scouters were able to locate and tell someone’s power level. Goku, Piccolo and the other Z-Fighters could sense a person’s power level or Ki and didn't need a scouter. The Frieza Force relied solely on scouters and couldn't sense Ki like the Earthlings or Namekians. After his battle on Earth, Vegeta learned to sense power levels without a scouter. Yet there were still times where he wished he still had a scouter, like when he was trying to locate the Dragon Balls.
He could sense Frieza’s massive Ki no problem. However, when he tried locating Gohan and Krillin who were also collecting the Dragon Balls, he couldn't sense their Ki as they could lower their powers to absolute zero. Something he was just starting to learn. In the fight against Frieza, when the tyrant transformed into his second form, he stated that his power level was over 1 million. Way higher than any previous power levels picked up by scouter that were in the thousands. When Goku was fighting Captain Ginyu, he powered up to a power level of 180,000. The highest power level shown on a scouter in the series history. After the Frieza saga, there wasn't use of scouters to read power levels, as the Earthlings and Saiyan’s on Earth can sense Ki, whether it was powerful or weak. Sensing Ki is something that started late in the original Dragon Ball when Goku trained with Mr. Popo on Kami’s Lookout.
In the movie Dragon Ball Super: Broly, Cheelai and other members of the Frieza Force used scouters. When they read Broly's power level, it was so huge that the scouter couldn't accurately rate it. The same thing happened to Goku and Vegeta when some other Frieza Force members were on Earth collecting Dragon Balls. It's proof that even high-tech scouters can't estimate a high power level accurately, and thus why power levels aren’t relevant in Dragon Ball anymore.