The latest design and trend begun from Apple's iPhoneX huge success though one of the new brands has released it first and unfortunately it could not become popular.
The Vivo and Oppo brought it the next with an extra size in notch design phones in comparison to the iPhoneX and later many other brands got released likewise.
The size of the notch is smaller in the Essential PH-1 smartphone that was actually released before iPhoneX, though there is a conflict in this matter as well.
Other reason for notch is, the smartphone brand is trying for some innovation and changes to attract more customers beside its full view display or bezel-less models and give them larger display in comparison to their earlier standard 5.5 inch phone model by increasing it to 6.2 inches.
The aspect ratio has also increased from 18:9 to 19:9 because of the notch design. The software too got adjusted a bit to give both the option for the notch users, like, top notch or just full view without notch (standard display), which the user have to select from the phone setting.