Carriers might hide signal strength from phone users beginning with Android P
This information in numerical form can be found on the SIM status screen in Settings on your Android phone in dBM. The abbreviation stands for "decibels relative to one milliwatt." A reading of -120dBm is said to be the minimal reading for a cellphone signal. A reading of -99dBm would represent a stronger signal. The numerical figures are translated into the infamous bars seen at the top of your handset. To get there, go to Settings > About phone > Status > SIM status.
Why this might be implemented is unknown at the moment. We also don't know which carrier (or carriers) requested the change. Keep in mind that this is not something that is going to happen very soon. After all, we are just starting to see some 2017 devices (like the Verizon Moto Z2 Force) receive the update to Android Oreo. This means you still have plenty of time left to brag about the number of bars on your phone.
source: AOSP via XDA