Because I don't need the launcher. I start most of the programs I need on boot and they go on for weeks until the next reboot (emacs, terminals, browsers, Thunderbird, keepassx, Telegram and 32 GB of RAM.) I use a virtual desktop (a Gnome activity?) per project so I have very few windows open per desktop and I alt tab between them. One browser window per desktop, one terminal per desktop, one emacs frame per desktop, Slack, etc. BTW, I wish that desktop Slack had an option to display multiple windows. Doing it in a browser is obvious but the desktop app is better than the browser one, so I drag it into another desktop when I change project.
I run the other programs by pressing the windows key and typing their name, not every day or week. What I use my bottom bar for is to access the icons in the notification bar. Glance at the time, open or close a VPN, take a screenshot with Flameshot. I also placed the favorites menu there (some extension?) to start the file manager. I'm using Nemo instead of Nautilus because I like to predictably access files and folders with type ahead. I occasionally use the bottom bar to click on the name of a dining program and it's nice to have see them side by side as in old Windows versions.
Actually, the screen of my laptops got only slightly wider in the last 25 years but considerably shorter. 16:9 is bad on laptops.
This means that an Ubuntu like launcher (on a side) should be optimal and yet it takes away the space I need to display two windows side by side.
That's why I always reconfigure Gnome to move the top bar to the bottom and merge it with a task bar. I also autohide it to gain some space.