Evie at the moment as it's very lightweight and responsive. Using on my Moto X4 with Andriod 8.1.2. Tested it with Andriod 9 (development).
For now I am using Microsoft Launcher. It is pretty good and the next one close I llike is Nova Launcher Prime I used in the past.
Nova Launcher Prime looks freakin sweet on my Galaxy S9 Plus. It is the only app I've ever paid for on Play Store, .
Was a long time Nova Prime user, now on Android P and Smart Launcher Pro 5, its fast and easy to navigate.
To have additional features and to customize your device / change its look, especially start / home screens and the app drawer. For instance icon packs, animations, gestures, icon dock, icon bars, widgets, folders, etc..... The early versions of stock android launcher or the proprietary launcher from Samsung (AKA touchwiz) were lacking of useful features... For instance gestures. One example: I have two internet browsers installed but only one icon chosen...(to have a tidy and slim appearance) If I push it FF opens. If I swipe it upwards TOR browser opens....the same I did with different apps who have the same purpose, though...(music players, messengers..etc) In the meantime the Samsung's touchwiz has been replaced by Samsung experience first and then by Samsung One UI... The current one is quite usable also the Android stock launcher is.... Anyway still people use an own launcher additionally. I myself have bought Nova launcher that time and I am still using it. I like to have my OS customized with an individual look to my likes and an own way how to have access to things......it's just like the girls having their own fancy cases for their phones....
Thank you... Once again I see what a completely different attitude towards digitalisation I have, compared to most other people.